Woooo!
"Woooo!" is the eighth episode in the fourth season of the television series How I Met Your Mother and 72nd overall. It originally aired on November 17, 2008.
Plot
Robin begins to tire of how Marshall is always around when she is spending time with Lily. Lily invites her to her friend Jillian's birthday party. They arrive at the party and are surprised to see it is being held in a western-style bar; they discover Jillian is a "Woo girl", a single woman who often goes out partying, nicknamed so because of their supposed tendency to constantly yell out "woo!"
After the party, Lily is surprised to discover Robin has become a "Woo girl", and is spending time hanging out with Jillian and her friends. Lily tries to spend time with Robin and her new friends, but does not fit in. Robin explains that this is because woo girls are sad people, with little to look forward to in life, whereas Lily is content and married. Robin explains she feels like one of these people, as she is both unemployed and single. The two resolve to spend some more time with each other without Marshall.
