If the first CW television crossover between "The Flash" and "Supergirl" back in March of 2016 sparked the superhero friendship, Tuesday night's musical revue cemented it with tap shoes.
Watching the jaunty episode titled "Duet" was like inhaling pure joy — a saccharine-saturated performance so ridiculously self-aware that both leads Barry "The Flash" Allen (Grant Gustin) and Kara "Supergirl" Danvers (Melissa Benoist) intermittently dropped character to look around the set, as if they too couldn't believe the charm of what they were creating.
Former "Glee" star Darren Criss was cast as antagonist the Music Meister. He popped into the last few minutes of a previous "Supergirl" episode and "whammied" (yes, whammied) Supergirl into the musical fantasy land. It was a place where everyone spoke with accents straight out of a high school production of "Guys & Dolls" and looked fabulous.
Naturally, Supergirl's National City "Scooby" gang were concerned about said "whammying," so they crossed over to the alternate dimension that houses Flash and his Central City compatriots. Fortunately, the Flash was also whammied by the Meister and — presto! — the musical crossover was set.
Although the rationale behind the villain's evil scheme wasn't entirely coherent — he wanted to drain their powers while making them understand love, or something? — it didn't need to be. Criss was put in this episode for two reasons: to look good in red suspenders and to sing. And he did both quite well.
But the true thrill of the musical debut was simply witnessing "The Flash" and "Supergirl" cast — many of whom have a background in musicals — get a prime chance to unleash their inner theater kid.
John Barrowman (a veteran of "Miss Saigon" and "The Phantom of the Opera") got a bit of camera time dancing and singing to the '60s pop classic "Put a Little Love in Your Heart." Jeremy Jordan (of the original Broadway production of "Newsies" and NBC's musical drama "Smash") was naturally paired with a piano. Victor Garber (whose stage credits include the original Broadway cast of "Assassins" and the 1990s revival of "Damn Yankees") got a short but sweet number, and then there was original "Rent" cast member Jesse L. Martin.
This isn't the first time Martin has graced "The Flash" with song, but we did not expect him to reappear in this alternate musical reality in a relationship with Garber (who started on "The Flash" but is now on "DC's Legends of Tomorrow") belting out "More I Cannot Wish You" from "Guys & Dolls" together. They were just a couple of theater-style gangster dads singing classic Broadway songs to their TV daughter, and that was stupendous. Why? Because it was ridiculous, and all heart.
And heart is one thing you can depend on from "The Flash" and "Supergirl." When these two shows commit to acts of adorableness, they go full basket of puppies. There is no in between, no treading water. There are only soft-shoe duets between superheroes with actual lyrics like, "I'm your super — that has a double meaning — friend."
If you're going to do a musical episode on television and compete with legendary greats like "Once More With Feeling" from "Buffy the Vampire Slayer" or "The Nightman Cometh" installment of "It's Always Sunny in Philadelphia," the key is to commit.
"The Flash" accomplished this by doubling down with a happy ending that wound up with the title character proposing to his love interest, Iris West (Candice Patton), through song. The number, penned by Benj Pasek and Justin Paul (who just won an Oscar for "City of Stars" from "La La Land"), hits hard when the world's fastest superhero starts crooning "Runnin' Home to You."
"Duet" was sweet, sweet cheese. It was a kitten delivering a Hallmark card with the words "you're purr-fect" spelled out in glitter. But it knew it and steered into the delightful.
In a TV world awash in procedural dramas and murder mysteries, sometimes it feels pretty great to take a song break.