These are all contemporary turn-of-the-century comedy TV series where each pairing shares at least one cast member:
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Spaced - You'd probably want to be reasonably familiar with UK pop culture of the time to truly appreciate it, but it's still somewhat entertaining even without that.
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Black Books - Sister series to Spaced. Probably not in the same universe, but shares some of the same cast. A bit more surreal and doesn't require so much pop culture knowledge.
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Green Wing - Turn the surrealism up yet another notch, add in a teaspoon of darkness, then set it in a hospital.
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JAM - Turn the surrealism dial fully around to the black setting, to the point of being outright disturbing and wrong.
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Big Train - Turn that dial back into silly and relatively light hearted... though you can tell there's something a bit troubling going on at the same time.
Outside that stable, but you may have watched:
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Babylon 5 - Top rated sci-fi. Some episodes can be a bit meh, but the ones that aren't are amazing.
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The Animatrix - Apocryphal short animations of various stories set in the universe of The Matrix, which you might want to rewatch first.
Yes, I have been under a rock since the turn of the century. I like it under here.