Sealed Evil In a Soda Machine

When a work—especially a Long Runner—is driven by multiple iterations of Sealed Evil in a Can, with a new can opened every season. Usually each such Evil has little or no relation to any other, and they do not build on each other's successes (if any) but go off on their own. One gets the image of the protagonists starting each season by metaphorically standing in front of a soda machine, inserting their cash, and getting a new can of Big Bad dispensed, ready to be opened.

This is a subtrope of Sealed Evil in a Can, obviously. Not to be confused with Sealed Evil in a Six Pack, which is when a single Evil is stored in separate parts, or Sealed Cast in a Multipack, which is when multiple players from all sides of a single plot are stored in different cans.

Anime and Manga

 * Pretty Cure has this in recent seasons: with Noise, Pierrot, King Selfishness, and Mirage.

Live-Action TV

 * Mighty Morphin Power Rangers is probably the Trope Codifier here, with a new sealed evil unsealed practically every season: Rita Repulsa, Ivan Ooze, the Demons from Lightspeed Rescue, the Orgs from Wild Force, the villains from Mystic Force, and more.
 * Super Sentai, from which Power Rangers was derived, did this as well—although not as often as its offshoot did, so it misses out on being the Codifier.