The Big Lipped Aligator Moment

The Big Lipped Alligator Moment is a running joke used mostly by the Nostalgia Critic. It appears when something in a movie/TV show comes by that is apparently random to the rest of the script's criteria, eg. a happy song and dance routine in an otherwise dreary and depressing drama. The first usage of this joke was used in Ferngully; The Last Rainforest

Description
According to the Nostalgia Chick, a 'Big Lipped Alligator Moment' consists of a scene or plot point that is unexpected, has little or no resemblance to the rest of the movie, and after the scene, is never again mentioned by the characters. The first example of this was used in a scene in which Zac, the main character, is ambushed and stalked by a lizard, who sings about eating him. Once the song has ended, it is never mentioned again, meaning that the movie could make more sense without the scene.