“Doppelgangers” is the final episode of How I Met Your Mother season 5. It is episode 24 of that season and the 112th episode overall, originally airing on May 24, 2010.
The episode centers on Marshall and Lily’s pact to start trying for a baby after seeing Barney’s doppelgänger. Barney first disguises himself as a cab driver, then as an Estonian street performer, but neither attempt truly satisfies the pact. Later, Lily mistakes a pretzel vendor for Barney’s double, and Marshall accepts the sighting because he realizes Lily is finally ready to have children.
The title continues the show’s recurring doppelgänger storyline, introduced earlier when the group discovers look-alikes for several main characters. The finale also explores how the friends themselves have changed over five years. A common mix-up is confusing this episode with a later-season finale; “Doppelgangers” closes season 5, not season 6 or season 7.