Mosbius Designs (original) (raw)

"Mosbius Designs" is the 20th episode in the fourth season of the television series How I Met Your Mother and 84th overall. It aired on April 13, 2009. In the episode, Ted starts his own architecture firm while Marshall is worried about his own employment situation. The episode also marks the beginning of Alyson Hannigan's maternity leave; Lily appears only in the cold open.