03E17 - The Goat

As he started comforting her following Simon dumping her for the second time in her life, Barney ended up sleeping with Robin. In the aftermath, both Robin and Barney want to pretend that it never happened. It ends up being seemingly easier for one than the other. Barney feels that his actions are making him looking guilty especially in front of Ted, to who he feels he broke his self-written bro code in sleeping with the ex of a friend. As such, Barney hires an unemployed Marshall to be his lawyer. Marshall's legal task is to go through the bro code to find a loophole that made it OK for Barney to sleep with Robin. Meanwhile, Ted's thirtieth birthday is approaching, for which the gang are throwing him a not so surprise rooftop birthday party. The party may be ruined by Barney and Robin's secret, and by Lily's new goat, which she rescued from slaughter. As Ted relates this story to his children in 2030, he admits upon completion of the story that he got a large portion of it incorrect.