Black Friday

In a musical about an Eldritch Abomination sparking Retail Riots across the globe, Act 2 of Black Friday begins with "Deck the Halls (Of Northville High)"; a song from the High School Musical pastiche "Santa Claus is Going to High School"; a choice even more jarring in the filmed version where the 15 minute intermission is replaced with a fade to black that lasts a few seconds.

Example of:
Irrelevant Act Opener