Grey's Anatomy: "Song Beneath the Song" (2011)

Throughout its seven seasons, ABC's medical drama Grey's Anatomy has had few light moments—from the traumas in the hospital to the dramas of their romantic lives. When its creator Shonda Rhimes announced plans for a musical episode last November, many were therefore skeptical about how the Broadway tropes would work on the hour-long show. But Rhimes had a formula to make the episode, which aired Thursday night, work— Grey's used songs from Snow Patrol, The Fray, and similar indie bands that were popularized in earlier episodes instead of trying to go the route of the Great White Way. The fact that Grey's boasts Tony-winning actress Sara Ramirez, who was featured in "Song Beneath the Song" in two different versions of herself, also gave cynics faith about how the actors would sound. While it certainly had its cheesy moments—as any musical does—the songs did ease the tension of an incredibly emotional episode.

Buffy the Vampire Slayer: "Once More, With Feeling" (2001)

Generally considered the gold standard of musical episodes, Buffy's "Once More, with Feeling" had the characters of Sunnydale spontaneously break into songs that expressed their deepest secrets and thoughts thanks to a demon who compelled them. The episode, which was written and directed by the show's creator, Joss Whedon, earned high ratings and struck a chord with die-hard fans, who largely consider it one of the best of the series. The Buffy musical episode is so beloved, in fact, that theaters began showing it as a sing-a-long—until 20th Century Fox put a stop to it, due to the high cost of actor residuals related to the replaying. Although Whedon had no experience writing musicals, his take led to a cult following. Considering it includes a song called "The Mustard"—in which the townsfolk serenade an effective dry-cleaning service—it's not hard to understand why.

Gilligan's Island: "The Producer" (1966)

A three-hour tour unexpectedly included a three-hour musical when the sudden arrival of a Broadway producer inspired Gilligan and his crew to put on their own production—a musical rendition of Hamlet—in an effort to convince him that bombshell Ginger is a talented actress. Of course, the producer managed to slip off the island without saving any of the castaways, but he did help the show earn its place on TV Guide's list of "The 100 Greatest Television Episodes of All Time."

Daria: "Daria!" (1999)

Although music had played a role on MTV's Daria—considering the eponymous character's longtime crush Trent and his band Mystik Spiral—it wasn't until the show's third season premiere that the angsty cartoon series went full-fledged musical. In the episode, Daria Morgendorffer's hometown, Lawndale, anxiously prepared for an upcoming rainstorm—which got all the residents singing and dancing. The musical element provided some interesting challenges for the cast since none of the voice actors were hired because of any singing ability. The voice of Daria, Tracy Grandstaff, was famous for being monotone and Wendy Hoopes, who provided the voices of Daria's best friend Jane, sister Quinn, and mother Helen, had to sing in three different voices. In the end, the cast pulled it off, and Grandstaff even called the musical episode her favorite of the whole series. "I am completely tone-deaf and I can't believe they talked me into doing it," she told the Village Voice. "So the fact that it exists is hilarious to me."

How I Met Your Mother: "Girls vs. Suits" (2010)

Both How I Met Your Mother's Neil Patrick Harris and Jason Segel are huge fans of Les Miserables and Harris claimed the two regularly perform the "Confrontation" song on set. So after Harris hosted the Tony Awards and Segel displayed his well-tuned abilities with his Dracula musical in Forgetting Sarah Marshall, it seemed only natural for their CBS sitcom to do a song and dance episode. Plus, Segel's on-screen wife is played by Alyson Hannigan, who previously performed in the musical episode of Buffy the Vampire Slayer. For the 100th episode of How I Met Your Mother, there were not only lots of clues as to the identity of the mysterious titular "mother," but also a rendition of "Memory" from Cats and an original musical number at the end, featuring Harris' character debating the eternal question that plagues many: girls or suits.

The Simpsons: "Elementary School Musical" (2010)

Over 22 seasons The Simpsons hasn't shied away from much—especially not music. The animated hit has had five song-filled episodes, largely featuring original compositions by esteemed TV composer Alf Clausen. Kicking off the show's current season was the musical episode "Elementary School Musical," parodying Disney's High School Musical and the Fox hit Glee. In fact, several talented voices from the latter series, including Lea Michele, Cory Monteith, and Amber Riley, contributed to the episode, in which young Lisa Simpson attends a performing arts summer camp. In keeping with the celebrity cameos, "Elementary School Musical's" songs were penned by comedic singing duo Flight of the Conchords.

Scrubs: "My Musical" (2007)

Before Grey's Anatomy crooned in the emergency room, the quirky comedy Scrubs found a brainy way to weave music into a medical series. The "My Musical" episode featured a patient who suffered a brain aneurysm and then sees and hears everything in the world around her through songs. The series regulars sang original songs in her imagination, but did not actually break into any unexplainable dance routines. The episode did, however, spawn the celebratory bromance duet "Guy Love," sung by doctors and best friends JD (Zach Braff) and Turk (Donald Faison), which quickly caught on. One reviewer noted, "'My Musical' could have just been a random gimmick episode of a great television program, but instead it was a logically insane episode which played to the series strengths completely."

Xena: Warrior Princess: "Lyre, Lyre Hearts on Fire" (1999)

In this musical installment of the supernatural fantasy series, Xena and her sidekick Gabrielle travel to Melodia, Greece, and organize a battle-of-the-bands style competition to decide who will win the coveted Golden Lyre. They performed anachronistic hits like "War," "(There's) Always Something There to Remind Me," and another inspired by Bye Bye Birdie. Of course, none of those songs existed in Xena's ancient times, but nevertheless, the cultish show did camp well—in fact, it was Xena's second musical episode, after 1998's "The Bitter Suite," which earned two Emmy nominations.

One Life to Live: "Starr X'd Lovers" (2010)

This soap opera's musical extravaganza, which aired over three days, featured song and dance numbers revolving around character Starr Manning's high school prom. From '80s classics by The Go Go's to current Top 40 hits from the Black Eyed Peas, One Life to Live showed range with its musical selections, keeping viewers and its stars on their toes. But if any genre can handle the absurdity a musical throws, it's soaps. Actress Kristen Alderson, who plays Starr, said she enjoyed performing the musical as much as One Life to Live's regular drama because of "the fact that you don't know whether you're going to be singing, or crying, or laughing or yelling on any given day."

Oz: "Variety" (2002)

The HBO prison drama Oz was certainly no Wicked but that didn't stop the show from embracing its musical side in 2002. In "Variety," the occupants of the prison stage a variety hour, with each performance becoming a musical act—a concept allegedly born out of necessity. The show's regular narrator, Harold Perrineau, was busily filming The Matrix sequels so the writers needed a back-up plan and the musical numbers were used in place of his narrations. Despite the show's graphic and serious nature, the musical format was not too much of a stretch for many of the regular cast members—including J.K. Simmons, B.D. Wong, and Tony-winner Rita Moreno—who were Broadway veterans. Between them, the cast paid homage to Tori Amos and Barry Manilow and took a break from the typical jail time sequences. "I guess we're all getting in touch with our inner Broadway diva," creator Tom Fontana told Entertainment Weekly at the time.

7th Heaven: "Red Socks" (2005)

Reverend Camden and his brood were essentially the modern day Brady Bunch, with an added dose of Jesus. So the only thing surprising about the squeaky-clean family partaking in a musical episode is that it took nine seasons to do it. For the Valentine's Day episode of its ninth season, the Camden clan is overtaken by emotions and thus, breaks into song. Stephen Collins, for example, who played the Camden patriarch, drew on his Broadway experience (he was in Broadway's Spamalot) to belt out "Love Is Sweeping the Country" while making pancakes. With the preachy life lessons and saccharine sentiments viewers were typically asked to withstand on 7th Heaven, the added musical element of this special episode seems almost torturous.

Plus: Check out more of the latest entertainment, fashion, and culture coverage on Sexy Beast—photos, videos, features, and Tweets.