Trivia: All of the creatures in baby Rapunzel's mobile are referenced later in the movie. The blue bird is the first creature she encounters after leaving the tower (it flies around her head when she sings "completely free"). There is also a white horse (Maximus), a chameleon (Pascal), a yellow duck (The Snuggly Duckling), and a cherub (the old man who dresses like an angel in "I've got a Dream").
Trivia: When Megamind as Bernard is in the library with Roxanne, the book he is reading ("Megamind Unmasked") has a description on the back of a self-help book entitled "The Happiest Me I Can Be". This is the same book that Metroman read (shown later in flashback) that caused him to decide to cease to be a hero. (00:43:30 - 01:08:30)
Trivia: In the scene after Hiccup finally gets Toothless' new tail fin to work, and the two are relaxing after they fly through the fire ball, the two are greeted by a group of tiny dragons. This little dragon was actually what Toothless was originally going to be, as he was in the book, until they changed him to a dragon big enough for Hiccup to ride to suit the movie. (00:46:15)
Trivia: When a pine cone falls out of a tree and hits Yogi in the eye, a "Wilhelm scream" can be heard.