Hidden Mickey
As Lilo introduces Stitch to her bedroom you will notice many drawings on the wall. In one seen you will see a vintage drawing of Mickey Mouse just above her bed.
Ode to "A113"
Near the end of the movie, Lilo is prisoner and Stitch tries to free her. He falls back to Earth and sees a truck (which eventually burns in lava). The truck's license plate number happens to be A113, which appears in Toy Story, The Simpsons, The Brave Little Toaster, A Bug's Life, and Family Guy. It was also the number of John Lasseter's (who worked on Toy Story, A Bug's Life, and The Brave Little Toaster) college dorm room.