Last week, a reader reached out to me on Twitter and said that they missed the happy Barry of Season 1, to which I replied that I missed the happy everyone from The Flash's first season. Powers were fresh and new, Barry was eating just mounds of sandwiches from Big Belly Burger. People did drunk karaoke. Funny movie references abounded as we wrapped our brains around the idea of a time-traveling speedster psychopath loving Ghostbusters.

The show has maintained some of that funny — Barry (Grant Gustin) and Linda Park (Malese Jow) trading forced hero/villain barbs in an effort to lure out Zoom last season is still a highlight for me — but the tonal drift has been steady as Zoom and Savitar each threaten some kind of calamity, be it very unclear (Zoom's whole multiverse thing) or very clear (Savitar killing Iris (Candice Patton)), and the response from Team Flash has been a kind of dourness and pessimism regarding the situation.

One of Flash's defining qualities at the onset was that it wasn't particularly grim, like its parent show, Arrow. And while the two shows still feel tonally different, the space between them sometimes feels like it's narrowing, and it's not a tone that completely suits Flash. And yet, the writers and producers keep leaning into it.

So please imagine my surprise when one of the show's executive producers, Todd Helbing, recently told TVGuide.com that "sometimes our cast is at the best, and our show is at the best, when it's more lighthearted episodes." Helbing said this in reference to this week's episode, "Duet," and he's so very right.

The long-awaited — and immediately fan-demanded once Supergirl arrived on the air due to both casts' singing skills — musical episode was a treat on the level of pure fun. There was singing! There was tap dancing! There was Barry being thoroughly amused by everything (Barry, no one claps at spontaneous songs in musicals, especially those by performed by gangsters)! There was Kara (Melissa Benoist) thinking everything was The Wizard of Oz! Basically, I cannot recall the last time I so thoroughly enjoyed an episode of The Flash as much as I enjoyed "Duet."

I could go on listing things I loved about the episode — Jeremy Jordan hamming it up as Grady, Carlos Valdes' killer delivery of both "This problem right here needs...someone with green skin and a sick-ass cape," and "Man, how did you get out of the cell?!", the reminder that Gustin and Benoist are basically a charisma atomic bomb when paired together — but the big thing that "Duet" demonstrated is that it's possible for The Flash to tell a story that's light and fun while still having a point.

Here, the point was the realizations that Barry and Kara needed to rethink the breakups with their respective others, Iris and Mon-El (Chris Wood). But instead of at least an episode's subplot of each of them being very mopey about the breakups in between fighting whatever villain of the week showed up to terrorize Central City and National City, Kara and Barry had their epiphanies through helping Iris and Mon-El's star-crossed musical counterparts.

There was no bad guy to fight that mirrored their self-doubts to bring about this epiphany. Vouching for love — and seeing singing gangster versions of Joe (Jesse L. Martin), Martin (Victor Garber), and Malcolm (John Barrowman) — helped them to realize that their decisions may not have been as well-thought out as they were in the moment they were made. Optimism about a better life and a better world, with those they care about in it, won the day the for each of them, and while Supergirl is still routinely operating in this particular gear, Flash should take this lesson and apply it to the show in Season 4 (it's probably too late to save Season 3 from its doldrums, but I guess we'll see as it enters the home stretch).

If there is one thing that hobbles "Duet" and its happiness-based resolutions, it's that they are too easy, at least in regards to Flash (I think it's too easy for Supergirl, too, given how angry Kara was in "Star-Crossed" and how quickly she goes to being all smoochy with Mon-el here, but that's a Nick Campbell — who covers Supergirl for TVGuide.com — problem for next week, not a Noel Kirkpatrick problem for this week). The episode does acknowledge this with Barry mentioning how easy things are in musicals, and that does provide the show an out, to a certain degree.

But this, for me, comes back to the issue of tone. Barry's ballad-based mea culpa about being a twit might've landed a bit if the show wasn't pretty serious and dark this season. As such, a quick and happy resolution almost feels like a cheat in this context. It's a welcomed cheat — even if I would've loved Barry being all, "Look, metahuman, I'd like to go back to watching Top Hat in my sadness hoodie, so can we wrap this up, please?" — but one that might've landed better if the show just kept a little love and light in its heart. You know, like it used to.

The Flash airs Tuesdays at 8/7c on The CW.

(Full disclosure: TVGuide.com is owned by CBS, one of The CW's parent companies.)