Most blackmail plots in comedy follow a very standard formula. Person A finds out that Person B did something bad, and Person B does not want Person C to find out. This usually results in Person A blackmailing Person B, and hilarity ensues. The plot thinkens in a predictable way: Person B has had enough of the blackmail, and comes clean to Person C.
Family Guy's appeal has relied on its type of humor, that usually consists of the absurd, nonsensical, and countless cutaways. In celebration of its 150th episode, the show did the complete opposite. The entire storyline, except for the brief introduction and the musical recaps, consisted of Brian and Stewie being stuck together in a bank vault.