Boy reads The Incredibles manga in a scene from Finding Nemo.
One of the problems in advertising is a lack of continuity in the brand narrative over the years. Each new campaign is created at different times for different purposes and, often, by different people and lacks common elements besides the logo. See how Pixar bridges the gaps between its own stories by inserting Easter Egg references to its past -- and future -- projects.
And in case you were wondering, yes, you can advertise on the other Easter Eggs.