Perfect Month is a plot used by Barney Stinson in 2019, hooking up with 31 girls for a month. It is inspired by Perfect Week. Several girls were seen in Last Forever - Part Two. It was ruined, though, by the last girl—Number 31, as Barney calls her—as she gets pregnant. Number 31 later gives birth to Barney Stinson's child, Ellie Stinson.