Tonight's 'Mash Off' episode of 'Glee' was a total doozy, good til the last drop with hot Top 40 covers and much-anticipated song blends (finally!), which was only the icing on the multi-layer plot cake that had us gasping at every bite. PopCrush has your recap!

Puck's especially in love with Ms. Corcoran following their unexpected lip-locking sesh. The bad boy launches into a performance Van Halen's 'Hot for Teacher' at the beginning of the episode, which at first, fools us into thinking he's daydreaming. We see him rocking out while the teacher gets a little naughty, showing off her sexy curves in high heels and teasing the young boys. Given that school was never quite like that for anyone else, it's not a big surprise when we realize he was imagining the scene and is actually performing for the New Directions in the choir room with help from fellow boys Finn, Blaine and Mike Chang with the sexy teacher nowhere in sight. In the end, Will applauds Puck's passion and questions his motive, to which he responds, "I guess I just, uh, dig Van Halen."

Rachel, Kurt and Brittany are still head-to-head and feistier than ever in the run for class prez, but lying about your fellow candidates isn't the answer, as they learn from Sue's mistakes.

Finally, Shelby and Will sit down to talk about the elephant in the room -- the fact that most of his talented girls have left New Directions for her all-girls group, the Trouble Tones. Because they're friends, Will suggests a "world war glee," i.e. a friendly competition between the vocal talents to bring them together, in a sense. The instructors lead their students into the auditorium where it's a full-on verbal war between the kids until the pair of teachers take the stage and launch into an acoustic rendition of Lady Gaga's 'You and I,' which we believe is a highlight of the episode. And boy is it nice to see someone else sing for a change! The feuding groups agree to work together, in a friendly way, for the first-annual McKinley High mash off.

Back in the choir room, Finn suggests giving the hot solo to the new guy, but he doesn't mean Blaine -- he means Rory. Later, after a heated insult war in the hallway with Santana, he gives a more exciting suggestion, which is a dodge ball war against the two singing groups. That afternoon, during the match, the sporty singers begin an 'unintentional' mash-up of 'Hit Me With Your Best Shot' and 'One Way Or Another’ (Pat Benatar / Blondie) as they pummel each other with big, red, rubber balls, but the fun comes to an end when somebody gets hurt.

Later, Finn stirs up more mud when he very loudly ousts Santana as being gay after they meet again in the hall, but this time, it's not fun and games and cuts her especially deep. When it's time for the two teams to mash off musically, the New Directions get the pick of the draw and get to go first, delivering a super classic rendition of ‘I Can’t Go For That / You Make My Dreams’ (Hall & Oates), led by Finn, who was a main character in the 'Mash Off' ep.

In a shocking moment in the school gym, Rachel drops out of the run for the class presidency to let Kurt take the lead, and tells the rest of the school to vote for him, too. Like nothing ever happened, they're best friends once again! In another heated moment, Quinn confronts Shelby about baby Beth and things get really hairy and the hot teacher says she can't allow the birth mom to see her daughter any longer -- but Puck can.

A fellow candidate in the run for Congress puts Santana's sexuality on TV for all to see, as his daughter overheard the breaking news in the hallway. As expected, the red flag sends Santana running and crying, given that no one is supposed to know (except us, of course). Back in the auditorium, the sexy Trouble Tones, dressed in all back, deliver an unmatchable match-up of their own -- two Adele songs blended as one, 'Rumour Has It' and 'Someone Like You.' At the end, a sparked-up Santana approaches Finn about outing her, only to end up slapping him across the face, resulting in the show credits.