November 19, 2009 at 1:19 AM EST

Alyson Hannigan tweeted earlier tonight about shooting a musical number for How I Met Your Mother, and the special guest she invited.

alydenisof: I asked Joss to visit today while we were shooting the musical number. He did. Joss + Musical = FLASHBACKS

alydenisof: I have to say I sound MUCH better now!!! (now that nobody is listening)

alydenisof: Luckily Neil does most of the singing!

alydenisof: Anytime I sing, it will be mostly filler.

That last tweet is so perfect, isn’t it? (Hint: It’s very similar to a line she sings in the Buffy musical.) Sigh. View Alyson Hannigan’s Twitter.

related: Dear Joss Whedon, Don’t Stop Believing A longtime Joss Whedon fan reflects on the past in a piece that is less of a structured argument and more of a hopeless love letter. Read it while you listen to “Hopelessly Devoted to You” by Olivia Newton John for the full effect.