1. "Oz"
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The episode: "Variety"
Why they're singing: There's a variety show. But that only accounts for the diegetic songs. The rest are performed in place of the standard narrator segments, just 'cause.
Why it's WTF: Oz is a gritty prison drama, one of TV's first MA-rated series. Also B.D. Wong does Tori Amos' "Leather."
2. "7th Heaven"
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The episode: "Red Socks"
Why they're singing: Because it's Valentine's Day. There's no better way to express your feelings for someone than through song. Even poorly sung song!
Why it's WTF: Aside from the fact that there's not a whole lot of singing talent here, this is another musical episode without any real explanation.
3. "Scrubs"
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The episode: "My Musical"
Why they're singing: The patient has (spoiler alert) a brain aneurysm that makes her imagine the doctors at Sacred Heart are performing a musical for her benefit.
Why it's WTF: Music and medicine generally don't mix. On the other hand, Scrubs' addition to the genre is still less out of place than the subsequent offenders.
4. "Chicago Hope"
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The episode: "Brain Salad Surgery"
Why they're singing: Wouldn't you know it? Another brain aneurysm. Seeing the doctors treating you as musical theater performers must be a standard side effect.
Why it's WTF: At least Scrubs was already a wacky series — Chicago Hope was a more straightforward drama, which makes these musical sequences all the more bizarre.
5. "Grey's Anatomy"
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The episode: "Song Beneath the Song"
Why they're singing: Did you guess brain aneurysm? Close! Callie suffers a traumatic head injury that makes her— well, you know the rest.
Why it's WTF: See above. There's something truly surreal about doctors singing beneath their surgical masks while they try to save a life. At least they're singing "How to Save a Life"?
6. "That '70s Show"
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The episode: "That '70s Musical"
Why they're singing: It was the 100th episode and Fez has a very active imagination. Really, that's about all there is to it.
Why it's WTF: Most people don't imagine full-blown musical numbers featuring their friends (unless they've had an aneurysm!) so it's at least out of nowhere.
7. "Xena: Warrior Princess"
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The episode: "The Bitter Suite"
Why they're singing: Magic! Xena and Gabrielle are stuck in the land of Illusia. That's as good a reason as any to have them sing their emotions instead of speaking.
Why it's WTF: It's really no stranger than the rest of Xena. This was a show that stayed grounded one week and went batshit crazy the next. That makes this episode both WTF and par for the course.
8. "Buffy the Vampire Slayer"
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The episode: "Once More, With Feeling"
Why they're singing: A demon named Sweet is in town. He forces people to reveal their darkest secrets and insecurities through song. And sometimes they dance to death.
Why it's WTF: It actually makes total sense within the Buffyverse. At the same time, sure, it's weird to see Buffy sing while staking vamps, regardless of the explanation.
9. "Even Stevens"
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The episode: "Influenza: The Musical"
Why they're singing: Ren has a terrible flu, and in her fever dream, she sees everyone around her in a musical. Again, not the standard side effect, but to each her own.
Why it's WTF: If you're sick enough to start seeing shit, you should probably go to a doctor. That plus little Shia LaBeouf singing makes this one of the stranger delights on the list.
10. "Fringe"
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The episode: "Brown Betty"
Why they're singing: Because it was FOX's musical week! Also Walter is very, very stoned. Most the episode is his reefer-induced imagination. Just say no, kids.
Why it's WTF: Few TV shows manage to combine genres the way Fringe does here — this is a musical, detective noir, and, of course, sci-fi. It's just a lot to take in, but it works!