Even legitimately great television shows have them: installments that just don't fit, don't work, or just out-and-out suck. Which ones would you like to wipe from memory? (Yes, BSG's "Black Market," we're looking at you.)

It's not that any TV show is "perfect" — they've all got their clunkers, it's just the nature of the beast. But there are a few episodes of a handful of beloved shows that are so bad they make you question your sanity for liking the show in the first place — like Battlestar Galactica's "Black Market," an episode so bad that even Ronald D. Moore thought it was a misfire and Lost's "Expose," which introduced Nikki and Paolo, the most hated characters ever to share such small screen time. Oh, and every episode of Heroes, beginning with the first season's air-ball of a finale. But which is the most egregious offender?