...or used characters or plots you have spent months or years developing. I've had a few I don't like because of this, the latest one being The IT Crowd, as I can't see my long going nerdcom project ever being taken up now, that greedy, hogging Linehan has gone and ruined it for me.
Also three shows at least stole my title, meaning I can never use them now.
This must be a common problem among aspiring sitcom writers, so what are your despised sitcoms for making your beloved, slaved over projects redundant and worthless?