By the time we were at the end of the film, I was beginning to think that there weren't going to be any love letters to Apple in Up. The credits, featuring Russell's Wilderness Explorer merit badges floating by on a typed page, began to look somewhat promising. Sure enough, I spied a stylized and stationary "Spinning Pizza of Death," the dreaded Mac OS X wait cursor, on a merit badge just about at the end of the credits.
If you go to see the movie (which you should; it's funny, action-filled, and great for absolutely any audience) be patient and sit through the credits. You'll be rewarded by the sight of a SPOD on the big screen (it's after the two nuclear merit badges). If you're an Up-aholic, you can also check out the Mac game or the $4.99US iPhone game (link opens iTunes).
Update: Slashfilm has a photo of the SPOD (BBOD, MOD, take your pick...) merit badge in a detailed post about all of the Easter Eggs in Up.