"World's Greatest Couple" is a hilarious How I Met Your Mother episode. In this episode, Marshall makes friends with Brad and they do a whole bunch of things that couples would do together. They are so cute and adorable together. It was so sad when Brad broke up with Marshall to get back together with his girlfriend. I love how Lily moved into Barney's apartment. I love how she made a deal with Barney that she'll pretend to be his wife to scare off women who want stay at his house. I give this episode a 10/10.