For everyone like me, watching The Office or Parks & Rec for the 97th time: great job! You've simply been training your brain to enjoy itself according to science.
There's a study from the University Of Chicago that reveals the really good reason we find such joy in watching shows or movies over and over again. Exposing our minds repeatedly to the same content helps our brain process exactly what's happening in the series and eventually watching and comprehending takes almost no mental effort whatsoever. Aha!
The study also points out the sense of nostalgia that an old show brings can boost dopamine and give us a good feeling!
You can check out the whole study ON THIS LINK