10. Total Eclipse of the Heart
Although Rachel may have meant well, Puck, Finn and Jesse were offended to see themselves triple-cast in her "Run, Joey, Run" music video at the tail-end of season one -- so much so, Jesse breaks up with her. The episode ends with the spurned Rachel singing a tearful version of Bonnie Tyler's "Total Eclipse of the Heart" as the boys leave, accompanying her vocals at times. We love Rachel's vulnerability and all her egocentric crazy, but how many times will we see her cry and sing simultaneously? Of all her emotional outbursts turned performances, this one takes the cake.
9. Singing in the Rain/Umbrella
In this wet 'n' wild mashup from early season two, Gwyneth Paltrow's Holly Holliday and Matthew Morrison's Will Schuester go head-to-head with the waterworks -- and not of the crying variety, either. The magnetism was palpable, Holliday's girls donning black raincoats and strutting about to Rihanna's hit "Umbrella," while Schuester's guys kicked and skipped about the stage on the classic "Singing in the Rain." The result? An almost seamless transition between songs that showed off the undeniable chemistry that Morrison and Paltrow's characters possessed. Our question: With all that water, someone should be making sure Artie's wheelchair doesn't rust, right?
8. It's My Life/Confessions Part II
While the "Glee" girls put in a valiant effort, their male counterparts ended up winning the mash-up face-off on season one -- at least they did in the minds of "Glee" fans, who have downloaded a few more thousand copies of the "It's My Life"/"Confessions Part II" combination than "Halo"/"Walking on Sunshine." Bon Jovi's classic arena rock anthem meets Usher's tell-all ballad in this (also pseudoephedrine-assisted) performance. Is it questionable and bizarre? Yes and yes. Does it entertain? Completely.
7. Poker Face
In an emotional climax of "Glee" season one, Rachel (Lea Michelle) finally fulfills her big dream: To come face to face with her birth mother. But when she finds out that mommy dearest (played by Idina Menzel) is the coach of competing team Vocal Adrenaline, things get more than complicated. In their departing moment together, Rachel and her vocal dynamo mom take down Lady Gaga's "Poker Face" in a stripped-down way that brings a completely new feeling to the dance track. Our response: Oh baby.
6. Halo/Walking on Sunshine
Yes, glee club is all about unity and teamwork -- but a little healthy competition doesn't hurt, either. In season one's sixth episode, the girls and boys split up and faced off against each other with choreographed mash-up performances. The girls created one spectacular combination of Beyoncé's "Halo" with Katrina and the Waves' "Walking on Sunshine," leaving the boys and Mr. Shue (Morrison) dazzled. Of course, that was due in part to the fact that both teams were using performance enhancers (given to them by none other than their teacher's wife.) With their bright yellow dresses and pseudoephedrine-induced grins, the girls took the concept of "glee" to its absolute extreme.
5. Somebody To Love
Rachel's departure from glee club in season one's fifth episode was thankfully brief -- the singer rejoined her classmates just in time to perform this group version of a 1976 glam-rock classic. While it's safe to say that Finn (Monteith) is no Freddie Mercury, "Glee" fans seemed to love his boyish interpretation of the song's freedom cry just as much as the Queen frontman's. Watch out for Mercedes Jones (Amber Riley), who delivers a killer glory note at the end.
4. Defying Gravity
Lea Michele is a Broadway-trained singer at heart, but we didn't get to hear the full extent of her musical theater chops until the first season's ninth episode, where Rachel and Kurt Hummel (Chris Colfer) battled it out for the chance to sing this "Wicked" ballad at sectionals. Rachel won out after Chris sadly botched the song's final high note, but the two paired up offscreen to record the official single, making for a powerful duet that fans loved.
3. Teenage Dream
When Kurt (Colfer) transferred to the all-male private school Dalton Academy due to bullying at McKinley early in season two, Gleeks were less than thrilled at the idea of their most fabulous New Directions member getting little time in the spotlight. But when "Glee" fans saw Kurt's new singing group, the Warblers, take on Katy Perry's "Teenage Dream" with crushing a capella harmonies, we thought, "New Directions? Who?" The Warblers, led by the dreamy Darren Criss, have shined brightly on the show ever since their first showing with "Teenage Dream," which reached No. 8 on the Hot 100 back in Dec. 2010, but no performance has stood up to the group's original appearance.
2. Forget You
"What would you know about Cee Lo? 'Cause you're, like, 40," Santana scoffs at Gwyneth Paltrow's Holly Holliday character in season two episode "The Substitute." "Top 40, Sweetcheeks," Holliday shoots back, launching into the censored version of Green's 2010 megahit "F**k You." Sure, it's not as soulful as Cee Lo's original, but what did you expect? Paltrow's version is just as fun, and most notably garnered her a spot performing alongside the tune's originator at the 2011 Grammys.
1. Don't Stop Believin'
The Glee cast's very first full-group number is still its most popular. No surprise, considering Journey's "Don't Stop Believin'" is a long beloved and often-downloaded tune outside of "Glee." But Rachel, Finn and co. still manage to deliver a fresh take on this anthemic '80s song about the power of sheer optimism. When the "Glee" kids sing, "Everybody wants a thrill," you get the feeling they may actually mean it more than anyone who's sung it before them -- and that's saying something.