Episode 7 of "How I Met Your Mother"
s01e07 Matchmaker

When a matchmaker with a 100% success rate turns Ted away because he is not compatible with any of the available women in her database, he is still determined that he is going to find his match. After getting information from the matchmaker’s computer, Ted pays a visit to a very cute, but taken, dermatologist in an effort to prove the prediction wrong that there are no women out there for him. Meanwhile, Marshall and Lily are obsessed with ridding their apartment of a critter.