Gotta Catch Santa Claus
(2008)

Trevor's trap to catch Santa works and he is caught, but Veronica lets him go after he proves he's the real Santa.

LaFreeze backs down and stops freezing everything when presented with a present by Santa, which is revealed to be the reason he is going into a rage in the first place.

It is heavily implied at the end that it was all a dream, until Trevor opens one of his presents. Inside is a chess set featuring LaFreeze as one of the pieces, which is impossible if it was a dream. Trevor then breaks the fourth wall and begins a monologue, directly telling the viewer that it is up to them to decide if it was a dream or not.

Thanks Salvatore!