Collections are only for trues movie sequels.

How is a 'sequel' defined? Take, for example, Director Ang Lee's 'Father Knows Best' trilogy, or Krzysztof Kieślowski's 'Decalogue'. Even though the characters in each film may differ, they all revolve around a series theme and can be considered a collection.

This is explained in the rules here.

I understand the rules, and I raised the questions and the previous examples precisely because there are ambiguities. The two series I mentioned are not sequels in the traditional sense, but they can still be considered collections.

The Decalogue (1989) is a valid collection due to this part of the rule : "Series of stand-alone films and mixed series marketed as proper sequels are also allowed as collections. These sequels are usually numbered and share a similar theme and/or an universe.".

I don't know the "Father Knows Best" movies. So, I can't answer for these ones.

The collections I added share a similar theme but are not numbered, and are still considered collections on other platforms. I hope they can also be considered collections here. Thanks anyway, I appreciate your explanation.

Collections on TMDB are a unique, self-defined concept. So Collections and other terms platforms such as IMDb/Criterion/MUBI use to group films may be completely different from TMDB Collections.

Honestly, the current “Collections” system should just be renamed to “Sequels”, because that’s what it actually is. The word “collection” suggests you can group related films—same universe, theme, or branding—but the rules say otherwise. You keep emphasizing only direct sequels with recurring characters are allowed, so why not just call it what it is?

It’s frustrating when stuff like Fast & Furious (with spin-offs) or Saw (with changing casts and loose continuity) are allowed, but something like Cloverfield or Eastrail 177—which are marketed and perceived as connected—isn’t. Either apply the rules consistently or just be clear that this feature is strictly for sequels, not general groupings.

A simple rename to “Sequels” would avoid confusion and stop people from wasting time trying to submit valid groupings that will just get rejected anyway.