The Incredibles Comic
A boy can be seen reading a Mr. Incredible comic book.
When the dentist is preparing to give Nemo to Darla and all of the animals start fighting to keep Nemo safe, there is a lot of screaming that alerts the patients waiting out in the lobby.
As the camera focuses on the shocked patients we can see a boy sitting on the couch reading a comic book. The comic book is actually about Mr. Incredible and has the picture of one of the posters used to promote the movie.
This easter also doubles as a “prediction egg” since Finding Nemo released more than a year before The Incredibles. Pixar is notorious for putting characters of their next movie into a preceding film like when they put Nemo (2003) in Monsters, Inc. (2001) or Lotso from Toy Story 3 (2010) in UP (2009)