Did you hear that? That loud popping noise is the sound of heads exploding all around the pop culture universe in anticipation of Joss Whedon and Glee getting together to put on a show. And is that Neil Patrick Harris guest-starring? Ka-boom, indeed. And this alignment of forces results in one of the series’ most focused episodes, titled “Dream On” and airing 18 May.

Whedon has never found the mainstream success many think he deserves. His series routinely rank among critics’ and fans’ all-time greatest, even though a relatively small number of people actually watch them. At first glance, Whedon’s predilection toward SF and urban fantasy seems a lousy fit with the peppy musical theater of Glee. However, the connection makes more sense if you’ve seen Dr. Horrible’s Sing-Along Blog. Whedon made that hour-long Internet sensation that with family and friends during the 2008 writers’ strike. Harris starred as the titular wannabe super-villain, who was caught in a love triangle with his archenemy. Just like in Glee, everyone was prone to breaking into song without warning (see also: the Buffy musical episode, “Once More, With Feeling”).

Even more helpful, Dr. Horrible delivers an important lesson for Glee, beyond the obvious one, that Harris should star in everything. Songs need to be rendered in the service of story, rather than the other way around. 

The first half of the freshman season still invested viewers in the world of Glee, using soapy plots like Terri’s (Jessalyn Gilsig) fake pregnancy, Emma’s (Jayma Mays) engagement to Tanaka (Patrick Gallagher), the football team and cheerleaders vs. the glee club, as well as Sue’s (Jane Lynch) feud with Will (Matthew Morrison). It was over-the-top, but it was fun. The songs were the cherry on top that made it unusual. 

The season’s second half has offered a series of meta-episodes, exploring Glee the phenomenon. It has, after all, created multiple revenue streams, convincing fans to shell out for both the cast versions and the originals of songs on the show, as well as tickets to see the cast in live concerts. And so each recent episode has delivered a soundtrack instead of a plot. Aren’t we supposed to be building up a David and Goliath-like collision between our underdog glee club and the powerhouse Vocal Adrenaline? We barely get lip service to that any more. The quadrangle formed by Rachel (Lea Michele), Jesse (Jonathan Groff), Finn (Cory Monteith), and Puck (Mark Salling) now exists solely to allow for more duets. Without energy put into the relationships, we end up waiting for the next song, as if we’re watching a variety show. 

Then along comes this week’s episode. Whedon’s directing stint might have been just another gimmick, like the Madonna episode. Instead, “Dream On” moves the series forward in significant ways. For one thing, the episode is more character-driven than others in this season’s second half. Even better, the music fits perfectly with the plot. Harris is amazingly good as Bryan Ryan, Will’s glee club rival in high school and now a school board member who is looking to cut budgets. Bryan and Will sing “Piano Man” in a bar, not as a staged number, but as a magnificent moment, convincing and moving. The same can be said of their dueling duet of the song, “Dream On,” during a community theater audition, is equally. And ditto for a duet between Rachel and Vocal Adrenaline coach Shelby Corcoran (Idina Menzel) on “I Dreamed a Dream” from Les Miserables. These performances are wonderful, but they also serve a greater purpose, shaping a fully realized world.