1. In A Goofy Movie, Mickey Mouse can be seen in the audience of the concert during the dance number between Max, Goofy, and Powerline.
2. The spinning wheel from Sleeping Beauty is seen in Rapunzel's room in Tangled.
3. A copy of Rapunzel sits on the shelf in Charlotte's room in The Princess and the Frog, in reference to Tangled being Disney's next movie.
4. Dumbo makes a cameo as a bubble toy in The Great Mouse Detective.
5. In Oliver & Company, Pongo makes a cameo during the song "Why Should I Worry."
6. Jock, from Lady and the Tramp, makes a cameo during the "Twilight Bark" scene in 101 Dalmatians.
7. Don Knotts' Henry Limpet fish character from The Incredible Mr. Limpet can be seen among the crowd at the end of the "Under the Sea" sequence in The Little Mermaid.
8. In Frozen, Rapunzel and Flynn Rider can be seen attending the coronation of Elsa.
But, there is also some debate that perhaps Tiana and Naveen attended the coronation as well.
9. Posters for The Jungle Book and Toy Story 2 can be seen on the baseball field in Meet the Robinsons.
10. Kermit the Frog is sitting in the crowd during King Triton’s grand entrance in The Little Mermaid.
11. A Chinese restaurant is named after Mulan in Lilo & Stitch.
12. One of the shadows summoned by Dr. Facilier in The Princess and the Frog looks very similar to Jack Skellington from The Nightmare Before Christmas.
13. Pumbaa from The Lion King can be seen during the “I’ve Got a Dream” scene in Tangled.
14. Scat Cat from The Aristocats also appears in Robin Hood.
Although his appearance might have been due more to budgetary constraints on the film, which forced animators to reuse sequences from previous Disney films.
And yes, that's his real name :(