All of the reasons you mentioned, and many more.
Well, personally, I wouldn’t say any of the reasons you mentioned. 
But that really depends on how you define the word ‘fan’. Is it enough just to really, really enjoy their movies and be excited for the next one to come out and to care about Pixar as a whole? Or do you have to go down the route of collecting stuff and watching the films many times over? I don’t do any of the things mentioned and, although I’m definitely not the biggest Pixar fan on the boards, I’d like to think of myself as a fan of Pixar. So I dunno.
I know that you don’t have to do everything. I’m a fan of Pixar, but yet I only do that stuff for one movie, Cars. (Anyone who know me well enough by now should’ve seen that one coming.) I think you just have to enjoy all their movies to be considered a fan.
Then that would make you a fan of the movies - not the animation studio. But to say that you are a fan of Pixar means that you are a fan of the title, the term, the word in literal sense, isn’t it? So, let’s be more specific for at least one time. For at least one time, instead of saying, “What makes a Pixar fan” which is semi-generic to the ear and eyes, let’s type for just one time, “What makes a person a fan of every aspect that is affiliated with the term, “Pixar?””
Now that makes it easier. To be a fan of every aspect that is related to the word, “Pixar” merely means that you are a fan of everything that has to do with “Pixar,” this very word, be it the movies produced by the company that has the word in its title, or the toys and merchandises that are also copyrighted under the abovementioned company.
Now, I know that sounds a little stupid, having to be a fan of a word, but it might make more sense to you when you think about this question: What makes a person a fan? Just a fan. Not a fan of Pixar, Disney, or whatever, but in its most naked, general definition, a fan.
According to Dictionary.com:
fan(2)
–noun
an enthusiastic devotee, follower, or admirer of a sport, pastime, celebrity, etc.: a baseball fan; a great fan of Charlie Chaplin.
Origin:
1885–90, Americanism; short for fanatic
Synonyms:
supporter, enthusiast, partisan, booster, addict.
fanatic
–noun
- a person with an extreme and uncritical enthusiasm or zeal, as in religion or politics.
So, what are the words used to describe a fan? Extreme and uncritical enthusiasm, zeal, devotee, follower, admirer. Basically, you could practically say you follow in the way of that specific item of interest, like a religion. You agree with the philosophy of it, and you would process it out as you practice it in your everyday life.
Now that’s a fan.
So, what is the philosophy of Pixar Animation Studios? From the website:
“Pixar’s objective is to combine proprietary technology and world-class creative talent to develop computer-animated feature films with memorable characters and heartwarming stories that appeal to audiences of all ages.”
Proprietary technology simply means the technology of Pixar Animation Studios. World-class creative talent literally means having the inept ability to think differently, but other than that, to be the best in thinking different.
Let’s not forget the memorable characters and heartwarming stories. So, if Pixar’s philosophy is having the talent and technology to create them, then a fan must practice that in everyday of his - or her - life, by writing stories that touch the hearts of people, not just stories that look cool, and by designing characters that leave people remembering them, not some scribble you place across a paper in your spare time.
Though this is simply my opinion, there is only one truth. Let’s work towards exploring that truth in this thread instead of wandering around blindly, feeling our way through opinions. It’s easy to make an opinion you are uncertain of its accuracy, but it’s much better to make attempts in working towards the truth.
Ironically, that, along with this whole post, is but yet another opinion. 
To be a total fan, I think, as lizardgirl said, it is good enough to really enjoy their movies and care about Pixar as a whole. You can be a big fan of Pixar without owning lots of merchandise or memorizing all the lines
I like to consider myself a big fan of Pixar. I find their films really entertaining and awe inspiring. Being an animation student, I like to study their films and analyze what exactly makes the films so great so that I can try and bring those same elements into my work. I may not own much merchandise or watch the films everyday, but I respect and look up to Pixar. They are a big source of motivation and inspiration to me.
I think you the individual defines what a fan of Pixar is. I mean, signing up on to this forum is one sign of your fandom already. But fandom can be expressed in very simple ways (saying you are a fan, watching and loving their movies) to very overexpressed ways (watching a movie once a day, purchasing any/all Pixar merchandise you see, etc). If you continue to love Pixar and their love for storytelling, then that is dedication enough already.
Now for me, everyone knows I am a huge (obsessed) fan of the Incredibles. Here are a few ways on how I express my fandom.
(Taken from the What makes YOU Pixar’s Biggest Fan thread)
Reasons Why I Am A Big Pixar Fan
-
I have seen all of their movies and have loved (almost) every one of them.
-
I am the biggest Pixar Nut in my whole family, knowing almost every Pixar movie by heart.
-
I know the classic traditions in each Pixar film (Pizza Planet Truck, A113, John Ratzenberger) and can point them out in each movie.
-
i go about every day of my life, thinking about Pixar, whether it is their films, shorts, employees, directors, actors, future works, and of course, Pixar Planet.
-
Speaking of which, I am an active member of the forums and post just about every day. And to add a little bragging right in here, I remain the top poster of Pixar Planet.
-
I have a Pixar Monopoly game and Pixar playing cards.
-
When ever my friends and I want to watch a movie, i always suggest a Pixar movie first (incredibles first of all)
-
I plan to make a Pixar music video on youtube in the future.
-
My dream is to voice act in a Pixar film (perferably an Incredibles sequel)
-
I have tried to create a strategy game using characters all across the Pixar Universe.
-
Everyone (friends and family) know that I love Pixar.
-
I have a Pixar playlist on my Ipod.
-
I use Pixar quotes frequently.
-
In a disney store, i spend like about 75% of the time there looking at Pixar stuff.
/////////\
Reasons Why I am a Big Fan of The Incredibles
-I have seen the movie on average of once a week (used to be once a day)
I have written about 6-7 fanfics on the Incredibles (all of which are highly rated, reviewed, read, and liked)
My youtube channel is what you call “Incredibles Videos Central”. THere, I favor all of the Incredible Incredibles videos and add every TI video I see on Playlists (currently, i have 4 playlists, over 600 Incredibles videos)
Speaking of which, I have made Incredibles music videos, all of which are highly rated, favored and viewed. (Be jealous )
I do an Incredibles search on google, yahoo, youtube, and other places every day.
I dream about the Incredibles often.
I own both full and widescreen version of the movie.
I know the movie by heart and know almost every odds and ends of it.
I have seen the Disney on Ice Show of the Incredibles.
I always look for TI stuff at Disney Stores, Target, Toys R Us, etc.
I own TI merchandise (shirts, figurines, mini-statues, video games, computer games, books, toys, action figures, soundtrack)
Every time I hear a song, i think which charater fits with this song.
I ask for TI stuff every Christmas and birthday.
I never miss TI on TV (ever)
I can play every song (pretty poorly, and with struggles) from the movie by ear.
I always have fantasize what a probable TI sequel would look like.
My first Girl Friend was pretty much a Violet Parr.
I try to imagine what the TI Heroes would do in other movies.
(I have more, but I can’t think right now)
you’re sure like me…except i just don’t have any money to buy merchs. 
I think all of us here are Pixar fans to some degree. It’s not really about what makes you a fan, but if you are a fan at all. Just because someone else may not like, say, Ratatouille, doesn’t mean that they should be forced to. They are still a Pixar fan in their own way.
In my opinion, to be a Pixar fan, all you have to do s not hate any of their movies. 
I personally have way too mch stuff, and every one of their movies is in my house. I freak out about every upcoming Pixar movie, whether it sounds good or not, I rant about J Katz twice a day, I’m addicted to the commentaries, I freak out(loudly) whenever the kids at my school says ABL or Cars is bad, when we play charades, if Toy Story or The Incredibles is involved, the person acting points to me, every fcebook avatar I’ve had has been animated, thanks to Pixar, I watch way too much animation, my family gets really tired of Pixar, I write poetry regarding Pixar almost daily, I send them letters, I have TI and TI:Rise of the Underminer video games, when I was little, I watched TS and TS2 every day, I watch The Incredibles often, pausing and zooming at every little detail, primarily background photos of Bob and Helen, I am a member of this site, my favorite colors are red, yellow, and orange, I have seven TI t-shirts, and one sweatshirt, about which I wrote a poem, I have a Buzz/Woody blankey I must sleep with, a Mr. Incredible doll I must sleep with, I have 2 TS posters, and one TI poster, the jokes in the Incredibles are mostly not funny to me anymore, I have dreams about being visited by Bob and Helen(yeah, really), I cry through both TS sequels, I cry that there isn’t a TI sequel, and, thanks to me, my little brother is an OCD Pixar fan now, like me. 
I enjoy the movies. I love to get lost in the intricate and vibrant stories Pixar tells.
I’m not a super fan like Virginia and The Star Swordsman, but I adore the movies. le shrug
Aw, rock-itpop, I think you’re a super fan! Just because you’re not a freak like me, doesn’t make you not a fan. It just makes you a functional human being. 
I don’t wanna be a functional human being! 
Well, you have to watch all of their movies for sure and be interested in their future projects. It also helps if you have Pixar songs on your ipod, get excited when you see Pixar merchandise in stores, and you dream about going to Emeryville.
Oh, and if you’re a member on Pixar Planet you’re a total Pixar fan! 
I don’t either. I’m already weird, but I make it worse on purpose by taking my obsessions out farther. Yeah. I can make a sandwich and bathe myself, but past that, I’ll never be normal.
You dont have to be a Super Fan of one movie to be a fan of Pixar. In fact, you don’t need to be a huge fan to be a fan. if oyu really like Pixar’s movies to an extent, then you can call yourself a fan.
Not really. As Kyle often crudely cites, “fan” is shorthand for fanatic.
[Copied from the Bing dictionary]
I don’t think saying the movies is crazy enough for that.
Haters would say I am a holder of extreme and irrational beliefs for Pixar!
To me, what makes a true Pixar fan is one who is unafraid to make criticisms of it.
Sure, it’s easy to be an adoring worshipper and buy all the merch, watch the movie 99 times in the theatre (if you can afford it), and create a million fanart, fanfiction, and fan videos about them. That’s a given, what the average 90% of fans do without thinking.
But to be a true fan with its best interests at heart, you must be willing to provide commentaries about its procedures, its business structures, the plot of its films, the animation, the people, the scandals, the successes. You must be able to take apart the studio and analyze the best and worst qualities without fear or reservations.
It’s like ‘tough love’ with your best friend. If you keep praising and gushing about someone, you come off as insincere, not matter how good your intentions. You must be brave to critique and accept the flaws, while highlighting the noble aspects of your friend. And occasionally, you have to take the p*ss out of him/her with some gentle ribbing (which is why I do parodies and mash-ups of Pixar films every so often, I’m unashamed to make fun of them every once in a while).
It’s easy to fork out a hundred dollars to support the show many times when it’s in cinema, or buy/trade all the movie tie-ins and toys (and I’m not trying to put down those who do, because financial support is one of the explicit ways to show your love for the studio). But ultimately, I appreciate those who take away something meaningful from the experience, and share the messages of the films with others, while creating discussions and debates about the studio and its films. It is the shared, the common, experience with others and the fan community, that makes Pixar what it is today.
That’s what my nicer friends would say.
TDIT, you make good points. It’s unrealistic to say a company/movie is perfect.
Hmmmmmmm Since i’m a t-shirt freak i would have to say wearing a t-shirt of pixar makes you a total fan, then there’s saying qoutes after qoutes