I knew that "Barney Stimpson" (in How I met your mother) used to be Doogie Howser (in Doogie Howser, MD, - late 80s sitcom, remember the clunky laptop at the end with the "message" for that episode? predates Carrie Bradshaw by a decade or so!)
Actor in both cases, Neil Patrick Harris: http://www.imdb.com/name/nm0000439/
Doogies's closing thougts via 80s blue screen laptop: http://www.youtube.com/watch?v=N1WnfMFUqWQ
and Carrie's version 2 decades or more later on apple (of course): http://www.youtube.com/watch?v=m_6wtILhM50
My husband was convinced it was this guy (older brother from Malcom in the middle): http://www.imdb.com/name/nm0557733/
I know I'm a nerd (with a good brain for faces) and I love being proved right :-)
Ha, ha and double ha!