10. Joey & Rachel's "Romance" - Friends
It's fair to say that Friends' best years were long behind it by the time it started wrapping up, but in order to introduce some additional last-minute tension ahead of the inevitable reunion between Ross (David Schwimmer) and Rachel (Jennifer Aniston), a Rachel-Joey (Matt LeBlanc) romance was randomly introduced at the end of season nine.
Thankfully the awkward relationship only lasted for all of four episodes, and though Joey did admittedly mention to Ross that he was in love with Rachel in season eight, there's no excusing the guy hooking up with the woman his best pal just had a baby with.
That both Joey and Rachel saw how upset and uncomfortable Ross was with the whole situation just makes it even worse.
There was no scenario where a Joey/Rachel love-in would be a sympathetic or satisfying "happily ever after," and it just served as lazy wheel-spinning until season ten could circle back around to the ending we all knew was coming anyway.
But it was the point where Friends stopped being an endearing character-driven comedy and truly raised the curtain to reveal the cynical machinations of big-budget sitcom TV, where it just has to keep chugging along at any cost.