As his 31st birthday nears, an all-nighter to try to get business has Ted realizing he may need to pursue another career than architecture. Meanwhile, Marshall tries to get him up to a rooftop surprise party.
Ted explains to his future kids how a series of unrelated events led to a chance encounter with a former girlfriend. Barney makes the 200th notch in his bedpost. Marshall goes overboard when he discovers GNB has a department that can make him charts and graphs.
Ted goes out on his own as an architect and hires an intern to help get things started, but all he helps himself to is Robin. Meanwhile, news of impending layoffs at GNB has Marshall looking for a schtick to make him indispensible.
Barney attempts to complete in a single day all the tasks from a list Ted made to prove the gang's not too old to do them. Meanwhile, he challenges Ted to complete a list of things they're too young to do yet.
Ted's college girlfriend reenters his life and leaves Marshall and Lily remembering how much they hated her, while Barney tries to steer the storytelling towards Marshall's forgetting his pants at work that day.