Nathan Fillion reunites with Neil Patrick Harris in 'Puppet Dreams'
The Castle actor appears in episode two of the How I Met Your Mother star's comedy web series as a doctor.
Puppet Dreams features Patrick Harris's daydreams dominated by puppets.
'Doctor's Office' sees Patrick Harris reunited with Fillion, following their previous appearance in Dr Horrible's Sing-Along Blog.
Speaking about the episode, Patrick Harris told The Hollywood Reporter: "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 that was interacting with the puppets as if it was a live variety show.
"It was intentionally blue, but was intentionally light blue. 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."
Neil Patrick Harris is currently writing a "nonlinear" autobiography.