Santana (Naya Rivera) and Mercedes (Amber Riley) creating a melodic melange of Adele on “Glee.” (Frank Micelotta/FOX)

A weekly assessment of “Glee,” based on its musical numbers.

This recap begins with an apology for its tardiness; due to a mishap with my DVR — an incident I have officially dubbed a “Glee”-mergency — I was unable to watch the episode in its entirety until this morning.

After having done so, it immediately became clear that I could not just blow off this week’s recap, not when “Glee” delivered its strongest musical episode of the season (including its 300th musical performance) and some significant plot developments.

Among those plot developments: Rachel dropped her bid for student council president out of deference to Kurt, who is now running on an anti-dodgeball platform; Puck professed his love for Shelby and ’fessed up about what he and Quinn tried to do to get custody of Beth; a feud between Finn and Santana bubbled over into a ruthless dodgeball game and Finn’s outing of Santana in the middle of the McKinley High hallway; and Sue Sylvester’s unsurprisingly negative campaign for Congress sparked a negative ad against her, one that criticized her for appointing a lesbian (Santana) as head of the cheerleading squad. In summary, there was no end to the bullying on last night’s episode. And in the end, it was the biggest bully — Santana — who ended up being the one most hurt by it. I

But enough about the morals of these “Glee” stories. Let’s get to the really fun musical mash-ups, several of which served as a valentine to ‘80s pop and yielded an impressive song-per-episode ratio of one per every 12 minutes of “Glee.”

More “Glee” by the musical numbers:

The First Time

Pot ‘O Gold

Puck (Mark Salling) and company: “Hot for Teacher”

Given the mohawked wonder’s burning passion for Shelby (Idina Menzel), it was inevitable that he’d lead a Van Halen serenade to the sub who gets his blood pumping. In fact, I’m almost convinced that this entire plot thread was created solely for the purposes of reenacting this famous Van Halen video, which younger “Glee” viewers probably did not pick up on at all, but was amusing to us semi-older folks, especially when Darren Criss replicated some signature, crotch-grabbing David Lee Roth moves. On the down side, this totally made me miss Waldo from the original video, a clip I have embedded below. Watch the full “Mash Off” episode, which opens with this performance, and compare the two. Grade: A-.

Mr. Schuester (Matthew Morrison) and Shelby (Menzel): “You and I”/“Just You and I”

The first mash-up of the episode, an attempt by the competing show choir sponsors to encourage healthy competition between the New Directions and the Trouble Tones, was surprisingly strong. Who would have thought that an early ‘80s wedding song favorite by Eddie Rabbitt and Crystal Gayle would mesh so well with the Lady Gaga-meets-Jo-Calderone hit? Grade: A.

Santana (Naya Rivera), Finn (Cory Monteith) and full company: “Hit Me With Your Best Shot”/“One Way or Another”

Continuing with the ‘80s theme, the episode’s pivotal, intense dodgeball scene was set to a mash-up of Pat Benatar and Blondie that made us all want to get up and throw a ball at something. Oh wait, that’s what actually happened when I realized my DVR wasn’t working. Still, very effective. Grade: A-.

The New Directions: Hall & Oates mash-up

As cute as it was to see Mike, Puck, Artie and Blaine in John Oates mustaches, I thought this was the weakest number of the night. The merger of “You Make My Dreams” with “I Can’t Go For That” was infectiously catchy; it just seemed like the New Directions would have gone for something less dated and more edgy if they really wanted to compete with the Trouble Tones. In other words, this sounded like something that Finn’s mom would have suggested, not Finn himself. But since I’m old enough to be Finn’s, um, awesome aunt, I kind of enjoyed it. Grade: B+.

The Trouble Tones: Adele mash-up

Given the emotional stakes raised by Santana’s outing, which happened in the scene right before this performance, and the fact that it marked the series’s 300th musical performance, this marriage of Adele’s “Rumor Has It” with “Someone Like You” was all the more powerful. Like these Tumblr posters, I am starting to think that maybe the Troubnle Tones do deserve to win sectionals more. Because last night, they were indeed all three Fs: fierce, femme, phenomenal. Grade: A+.

Now it’s your turn: rank last night’s “Glee” numbers from best to worst.