I've never seen How I Met Your Mother, but I used to watch NPH on Doogie Howser when I was a kid. The monologue was kinda funny: basically the cast members telling him bad "how i met your mother" jokes. The better sketches of this episode were the "save broadway", 2 air traffic control women with extremely long fingernails, and the roland burris opening. The Penelope at group therapy skit was funny. Kristin Wiig is great!!
i didn't really care for the "frost/other people" (satirizing the frost/nixon movie) or the skit about people with 2 first names (Neil Patrick Harris, jamie lynn spears, etc.). Also, the skit about the Today show was not that good, except Neil was hilarious as a Richard Simmons-like aerobics instructor.
But the best skit was the digital short, with NPH playing the Doogie Howser theme on a keyboard, and the cast members joining in on other instruments, and all dressed like Doogie. Classic!