09/28 - Episode 2.05 - World's Greatest Couple [Airing October 16]: Marshall tries to adjust to being single, doing brunch by himself, but is embarrassed by the host at a restaurant when it becomes apparent that Marshall is by himself. He becomes friends with a man named Brad, who then gets back together with his ex-girlfriend, Jill, leaving Marshall alone again. Barney meets and spends the night with a beautiful young lady named Dawn, yet he is terrified in the morning when sexy Dawn turns into a clingy, yoga-doer who admits to falling in love with him. Lily walks in, Dawn assumes she is Barney's wife then storms out angrily. Barney decides to use this to his advantage and tells Lily to stay with him for awhile to keep that from happening again.
Source: SpoilerFix.com