Easter Eggs Page 1
The two old men in The Incredibles (2004) are Frank Thomas and Ollie Johnston, cameos of the final two living members of Walt's 9 Old Men of animators.

"...There's no school like the old-school!"
There's a Mickey Mouse watch on the wall of The Rescue Aid Society headquarters in The Rescuers (1977).
Upon King Triton's entrance during the rehearsal in The Little Mermaid, Mickey, Donald, and Goofy can be seen in the audience.

Along with Kermit the Frog.
In the background of the Hey Arnold episode, "Weighing Harold" (S4E68), there are two comic books with the titles CatDog and SpongeBob.

(SpongeBob being a series that hadn't even aired yet at the time.)
There is a Mulan poster on the wall of Nani's room in Lilo and Stitch.
Looney Tunes started out as a series to showcase music that Warner Brothers had recently received the rights to.

Hence the spelling of Tunes.

(Unaffiliated Advertisement)
(Unaffiliated Advertisement)