Step Brothers

Step Brothers is a 2008 movie produced by Judd Apatow and starring Will Ferrell and John C. Reilly, where two slacker adult children, Dale Doback (Reilly) and Brennan Huff (Ferrell), are forced to live with each other when their parents get married, after a Freudian Slip by Dr. Robert Doback (Richard Jenkins). Hilarity Ensues as they become best friends after suffering from hilarious hijinks, committing beautiful singing and rightful child abuse. (They deserve it in context).

This film includes examples of:

Adult Child: Both Brennan and Dale are this to the extreme, being 40-somethings who still live with their parents and act like 13-year-olds.
Berserk Button: Don't ever, ever, EVER touch Dale's drum set.
Black Comedy Rape: When the brothers first fight over the drums, Dale claims Brennan was trying to rape him.
The Cameo: By Seth Rogen and Phil La Marr.
Crowning Music of Awesome - In-universe, the brothers think their first company's music video is this.
- Later, we get a real one, when Brennan sings Por Ti Volare.
Fantasy Forbidding Father: Justified in that the two main characters are middle-aged and should be beyond such things.
Freudian Excuse: Brennan is a Man Child due to having his Jerkass brother getting the entire school to sing "BRENNAN HAS A MANGINA" during his school performance. Even the parents and faculty joined in.
For Science: One of Prestige Worldwide's stated goals.
- "We put liquid paper on a bee. It died."
Freudian Slip
Hilarity Ensues
Jerkass: Derek.
Kids Are Cruel: The kids led by Chris Gardocki who beat up Dale and Brennan and force Brennan to lick a dog turd. Dale and Brennan get their revenge in the end.
Poor Mans Porn: Brennan whacks off to a female gymnastics video in the intro.
Stylistic Suck - "Boats n' Hoes".