It may be hard to remember your first real obsession because you may not have been aware of it fully in a way, but there is that show that you truly remember as your first obsession. Mine came in my early 20s with the arrival of Babylon 5 where it really took advantage of serialized storytelling where, if you were like me, you had a hell of a time trying to catch each episode or hunting up reruns of certain episodes you missed through various overnight showings. The syndication for this series was terrible in a lot of parts of the country and trying to deal with it being bumped for sports or other events made it even more frustrating. But you could not miss an episode and just had to find it, read about it, engage with others about it if you were able to. This was one of those usenet heavy discussion shows back in the day for me – back when I used to DM a shared-world text MUD that had a discussion board component – and I couldn’t get enough about it.
Bonus Question: What show was someone else’s obsession that they got you hooked onto as well?