'Dr. Horrible' Reunion: Nathan Fillion Drops by Neil Patrick Harris' Web Series (First Look Video)

It's a Dr. Horrible reunion!

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Inside Neil Patrick Harris' Passion Project 'Neil's Puppet Dreams' (Q&A)

Nathan Fillion drops by in the second episode of Neil Patrick Harris' web series, Neil's Puppet Dreams, which features the How I Met Your Mother star dreaming in puppet.

For the installment, titled "Doctor's Office," Harris wanted the three-minute episode to veer toward classic Muppet Show.

"We planned to be much more like a Muppet Show sketch where we had elevated sets and a bunch of puppeteers were down below and a human actor was interacting with the puppets as if it were a live variety show," Harris told The Hollywood Reporter.

The episode starts with Harris reading a Canadian magazine, Canadian Life, and of course, he can't help but pay homage to some of Fillion's credits: "Are you kidding? This place is a Castle! Gives me a real sense of Serenity!" (Mentions of Desperate Housewives and, of course, Dr. Horrible's Sing-Along Blog are also made.)

"Doctor's Office" plays like content one wouldn't regularly see on a network.

"It was intentionally blue, but was intentionally light blue," Harris said with a laugh. "The whole joke at the end is none of it is relating to genitals at all. We pushed the boundary for sure. That's kind of The Muppets, [Jim] Henson-style of comedy that I always loved. The double entendre, if you will."

Watch the second episode of Neil's Puppet Dreams below:

New episodes premiere every Tuesday on the Nerdist YouTube channel.

E-mail: Philiana.Ng@THR.com
Twitter: @insidethetube