Oh my gosh, I gotta say I'm a sucker for the Monster of the Week trope. The modern media industry kinda avoids it more these days even going as far as advising show pitches to stray away from it entirely. But... flip, I can't help but kinda love it, even if it ususally devolves into weak writing.
Anyway for those that don't know, Monster of the Week is a show style that uses a new monster, baddie or alien as the center conflict of every episode. Power Rangers, Pokemon, and Scooby Doo are probably the most cut-and-dry examples of the trope in action.
Although my favorite shows always twist on this cliche, turning each conflict into a larger story rather than isolated events. ;D I'm lookin' at you Steven Universe.