John Ratzenberger is in every Pixar film, Am I right?
Yup, here, I’ll post his roles
[spoil]Toy Story (2) - Ham
A Bug’s Life - P.T. Flea
Monsters Inc. - Abominable Snowman/Yeti
Finding Nemo - The school of (I forget) fish that give Dory and Marlin directions
The Incredibles - The Underminer
Cars - Mack the Semi
Ratatouille - Mustafa, the waiter (hard to recognize)
Wall•E - John
Up - Tom the Foreman[/spoil]
He’s Pixar’s “good luck charm”, so they have him voice 1 minor (or in the cases of Wall•E, Toy Story, and Cars, somewhat more important) role in their movies
In Monsters Inc., he voiced [spoil]Yeti, not Sanderson.[/spoil]
Oh yeah, duh, I’m an idiot. XD How did I get that wrong?
I love how they have him in the movies, it always makes me chuckle when I hear him in the films, and it’s always fun to keep an eye (or an ear) out for him in new films.
I like the consistency of having John Ratzenberger in all of Pixar’s films; whether minor or major parts. Just like finding the ‘in-jokes’, it’s fun to find out who he’s voicing in the films. Makes me smile every time I hear him. 
He has such a distinctive, likable voice too.
The one that really got me was [spoil]Underminer in “Incredibles.”[/spoil] I’d been watching the movie, totally into the story, not even realizing, “Hey, where’s John?”, then at the last possible minute… I was cracking up!
That’s one of the things I really like about “Ratatouille” - it was fun hearing both John R. and Brad Garrett doing roles that were so different from their previous Pixar films, and in which they weren’t instantly recognizeable.
Yup, you got that right! Every one. I need to add that to the list of why I love Pixar 
Well it is interesting to note that Cars was really the only pixar movie where he had more than a couple of lines almost as if was the support lead being Mack.
I wonder if Pixar will indeed have him as a main character in future releases.
Uh, how about Hamm? 
P. T. Flea was a good role, too, as was Mustafa (the waiter) in Ratatouille. Really, he’s had some pretty good, albeit supporting, parts for Pixar.
Hamm will always be Ratzenberger’s most iconic role, but I think his other best characters are P.T. Flea, The Yeti, The Underminer (despite being thrown in at the very last minute), and Mack. I also like John in Wall-E because technically he got to play himself.