Aside from the obvious (John Ratzenberger), many Pixar films contain the same actors. For example:
Bonnie Hunt is in A Bug’s Life, Cars, Toy Story 3, and Cars 2
Jeff Garlin is in WALL•E, Toy Story 3, and Cars 2
Richard Kind is in A Bug’s Life, Toy Story 3, and Inside Out
Any more?
Are we including Pixar employees in this one? Well, if that’s the case:
Teddy Newton
Pete Sohn
Bob Peterson
Elissa Knight
Yes, they and others do scratch voices and sometimes end up keeping them. That is why you’ll sometimes see their names in the additional voices section fot the end credits. (Well said!)
Yeah, there are PIxarians.
There are people whose scratch records just…stick. Like Joe Ranft.
Pixar does like bringing back actors some, however. Brad Garrett is another.
I think Andrew Stanton and Pete Docter also appear in more than one film.
Didn’t Stanton voice a fly in A Bug’s Life with John Lasseter when they said “don’t look into the light!” “I can’t help it, it’s so pretty” 
Obviously we know he voiced Crush in both Finding Nemo and Finding Dory.
As for Pete, he voiced the Campmaster in Up, and one of the emotions (I think it was Anger) in Riley’s dads head in Inside Out.
Also Sigourney Weaver makes a couple of appearances in both Wall-E and Finding Dory 