Revealing mistake: At one point in Heat Miser's song, he eats two fireballs. Directly above the second fireball you can see the reflection of string used to hold it up.
A Year Without Santa Claus (2006)
1 revealing mistake - chronological order
Directed by: Ron Underwood
Starring: John Goodman, Ethan Suplee, Dylan Minnette, Chris Kattan
Audio problem: When the kid's dad and Santa are singing about believing in Santa their mouth movements do not match the music well.