CBS

Season 4: Episode 9 - The Boyfriend Complexity

The Boyfriend Complexity: ­When Penny's dad comes to visit, Leonard discovers that she told her parents they were back together because Leonard was always their favorite boyfriend of hers. Leonard takes full advantage and plays his boyfriend role to the hilt to Penny's dismay. Raj is disappointed when Bernadette shows up during his and Howard's quality time but they end up bonding more than Howard would like which forces him to put a stop to it in a very awkward way.