The actor's legal name is Kalpen Modi. He's best known to film and television audiences for his roles in "Harold and Kumar" and "House."
He's also no stranger to the White House. Penn worked previously for Obama in the White House's Office of Public Engagement. He was a major draw last year at the Democratic convention with a good-humored speech asking voters to stay engaged.
The actor returned to the White House in July along with singer Jennifer Hudson and actress Amy Poehler to promote Obama's health care law.
Obama made the announcement Monday.