Santana (Naya Rivera), Mercedes (Amber Riley) and Brittany (Heather Morris), stoking a “Disco Inferno.” (Adam Rose/FOX)

After deftly handling a “Grease” classic earlier this season, “Glee” turned its Travolta-related attentions to “Saturday Night Fever,” the 1977 movie that sent untold fingers pointing straight for that big disco ball in the sky.

This week’s episode-long “Fever” homage — like Mercedes’s performance of “I Will Always Love You” that, coincidentally, aired just days after the death of Whitney Houston — comes at a timely moment. With Robin Gibb of the Bee Gees in the headlines after falling into a coma, the “Glee” kids unintentionally chose a significant week to sing-and-boogie the praises of the disco era soundtrack dominated by Robin and his brothers, Maurice and Barry. (Next week’s full-on Whitney Houston tribute will only continue that tradition, this time intentionally.)

So what was the frayed shoestring of a narrative that tied together all those “Saturday Night Fever” numbers?

It revealed itself whenWill Schuester issued this mission to the seemingly goal-less Santana, Merecedes and Finn: “Your assignment for the week: perform a song from ‘Saturday Night Fever’ and then share your hopes for the future.”

Such a weird coincidence: I was given the exact same assignment in my high school AP English class, which is how I wound up humming “A Fifth of Beethoven” in front of 30 of my peers, then confessing that I’d like to become an MTV VJ.

Sorry, got too personal there. The point here is that this decidedly bizarre bit of homework led — spoiler alert — Mercedes to think more about how much she wants to become a diva (total Whitney Houston episode segue!); Santana to realize that she wants to be famous, then realize she actually she doesn’t want it enough to resort to releasing sex tapes; and Finn to decide that he wants to go to New York with Rachel and take classes at the Actors Studio. Yes, the same one from “Inside the Actors Studio” with James Lipton, a show on which, coindentally, the “Glee” cast recently appeared. (I can’t wait to hear Finn Hudson eventually tell us what he’d like to hear God say when he arrives at the pearly gates.)

. Oh, and the homework also led to performances of a number of “Saturday Night Fever” hits. Let’s assess them, shall we?

“You Should Be Dancing” — Blaine, Brittany and Mike

Is this a dream sequence? If not, why is there a disco ball in the classroom where this number begins? You know what, it doesn’t matter. This Bee Gees cover provided the perfect showcase for the smooth moves of Darren Criss, Heather Morris and Harry Shum, Jr. I liked their hitchhiking thumb gestures, I liked their fake hair-washing move and I was especially imprssed by Criss’s toe-touch, cheerleader jump. Grade: A.

“Night Fever” — Cast

The New Directions kids think that disco sucks. Honestly, I’m not sure most contemporary teens would have an opinion one way or the other about disco. Either way, it doesn’t matter because they totally changed their minds in 10 seconds once Mr. Schu and Sue Sylvester busted out a light-up disco floor that they clearly bought at Home Depot, then showed those whipper snappers that they both have night fever and know how to show it. I was kind of digging the whole thing until Finn did what is, officially, the whitest John Travolta impression of all time. Cory Monteith is a doll, but his “Saturday Night Fever” pose belongs in the Caucasian Awkwardness Hall of Fame. Grade: B.

“Disco Inferno” — Mercedes

Amber Riley looked pretty fantastic with feathered hair. Also, she sang the hell out of this song. Nothing else to say but grade: A.

“If I Can’t Have You” — Santana

Naya Rivera did a perfectly nice job of singing this Yvonne Elliman track. But the number’s success was marred by its too-familiar choir room staging. There wasn’t much in the way of choreography, and the only drama came from loving glances between Santana and Brittany and wistful looks exchanged by Rachel and Finn. Grade: B-.

“How Deep is Your Love?” — Rachel

Lovely vocals by Lea Michele, nice back-up by the perpetually present jazz band and a sweet premise — that Rachel was finally willing to show some generosity to Finn and encourage him to consider his dreams first. Nothing earth-shattering, but a cute enough number. Grade: B.

“Boogie Shoes” — Wade

Wait, who is Wade, you ask? Why, he’s the random Vocal Adrenaline member invented to give a third contestant from the “Glee Project” — that would be Alex Newell — a place on “Glee.” Fortunately, he demonstrated that he deserves to be in the mix by playing a cross-dressing teen who wasn’t afraid, despite Kurt’s and Mercedes’s concerns, to throw on a dress and some glittery high heels and perform a K.C. and the Sunshine Band tune. He was great. But would audience members in a Lima, Ohio auditorium really applaud him so quickly and unabashedly? I’m not sure. The fact that they did is no knock on Newell’s effectively energetic performance, but it did make his decision to go full-on “Priscilla Queen of the Desert” seem less brave than it really was. Grade for performance: A. Grade for realism: C-.

“More Than a Woman” — Finn and company

Monteith had some strong moments on tonight’s show, especially when he made that speech about how he just wanted time to stop so he could stay in high school longer. The guy’s at his best when he doesn’t have to sing or dance. Here, he had to do both, while employing a Bee Gees-style falsetto that I will refer to henceforth as a Finn-setto. It was a bit much. Also, Kurt's ‘70s hairdo made him look way too much like Mike Brady. Grade: C.

“Staying Alive” — Santana, Mercedes, Finn and cast.

A lot of white polyester suits, a lot of quick edits and, again, a heavy dose of Finn-setto. Grade: C+.

Do you agree with these musical number assessments? Weigh in by posting a comment.