Marshall Eriksen (Jason Segel) is Ted's college roommate and now best friend in How I Met Your Mother. Marshall is engaged to and eventually marries his college sweetheart, Lily.
Marshall is a lawyer who always wanted to work as an evironmental lawyer but in an effort to provide for his wife and future family now works with Barney at a big bank corporation.
Marshall was previously Ted's roommate for the first few seasons but now lives with Lily in their own condo they purchased.
Barney: Barney Stinson is back on the market. Mothers, lock up your daughters. Daughters, lock up your MILSWANCA's.
Ted: Oh wait, I can get this. Mothers I'd Like to Sleep With and Never Call Again
Barney: Correct, circle gets a square
Lily: So if those guys pressure you to smoke, what do you say?
Marshall: Only when I'm drunk.
Lily: Good boy