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.

Examples of Sealed Evil In a Soda Machine include:

Anime and Manga

Sailor Moon is probably the Ur Example, with a different foe every season/film, unrelated to each other.
Pretty Cure has this in recent^[when?] 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.

Web Original

The SCP Foundation is this Trope. A large percentage of the dangerous abnormalities they Contain are sealed evils that got lose somehow, and they either have to keep them sealed or re-seal it with their own resources. Ironically enough, at least two SCPs are actual vending machines that disperse products that May Contain Evil.

Western Animation

The Smurfs had this problem, always seeming to uncover ancient evil that had been locked away. There was the Jerkass Genie Genie Meanie from "Magical Meanie", Mystico the goblin from "Nobody Smurf", the Druids from "The Smurfs' Time Capsule", and the Mad Artist Maestro in "Every Picture Smurfs A Story" to name a few. Given his advanced age, Papa Smurf was often the one who imprisoned a lot of these villains in the first place.
In the first episode alone of the 2017 reboot of Duck Tales, Scrooge's three nephews and Webbie accidentally release three ancient evils, which Scrooge oddly keeps in his garage for some reason: the Deus Excalibur, the Headless Horse Ghost, and Captain Peghook, and even worse, all three of them team up! And Scrooge has barely finished scolding them for doing so when another accident releases Pixiu, the Gold Hunting Dragon. Later episodes have stuff like this in spades, including the Pharaoh Toth-Ra, the Bombie, and recurring villain Magica DeSpell. In many cases, Scrooge was the one who sealed these villains in the first place.
Jackie Chan Adventures actually acknowledges this and explains it's due to Jade's decision to kill the Big Bad of the first season instead of seal him again and how magic works in this series. Even after season 3 ends with the original Big Bad Back From the Dead and then sealed properly the conflicts of the following two seasons were set in motion from stuff he did when he was dead.