42

The number 42 is consistently included in many of >Pixar's films.

Possible Explanations
One possible explanation can be a fascination with Douglas Adams' Hitchhiker's Guide to the Galaxy. In this book series, the significance of the number 42 is that it is the answer to life, the universe, and everything. Another possibility may be an idolatry within Lewis Carroll's work, Alice in Wonderland and the sequent Through the Looking Glass, and What Alice Found There, where 42 is a crucial number. It represents Rule 42, the oldest rule in the book, and states: "All persons more than a mile high to leave the court." Douglas Adams, furthermore, drew inspiration from Carroll's masterpiece in constructing his own.

Finding Nemo
It is found in the address of the dentist, Philip Sherman: 42 Wallaby Way, Sydney, Australia.

Cars
Lightning McQueen says 42 while stating how many cars are on the track in the introduction. However, in the actual race, we only see 36 cars racing each other.

WALL•E
Before realizing he is late for the morning announcements, the Captain's screen reports 42 seconds on the clock before immediately turning to 43.

Buzz Lightyear of Star Command
The number of Buzz Lightyear's star cruiser in this series is 42.