Ranking All Of Penny's Ex-Boyfriends From The Big Bang Theory

While Doug (Allen Nabors), who was featured in only one episode of the show, "The Fuzzy Boots Corollary," might not technically count as an ex-boyfriend, he was still involved in a pivotal moment in the series. Penny went on one date with Doug, and the two are wrapping things up outside her apartment when Leonard approaches with some of Penny's mail that was mistakenly delivered to his home. Doug looks away from Penny, utters his one line ("What's up, bro?"), and goes back to trying to plant a kiss.

It turns out that, while Doug didn't have what it takes to be a boyfriend, his existence did prompt Leonard into asking Penny out on a date. Leonard was passionate about Penny from the very beginning of the show, and the two would go on to date off and on throughout the run of the series before ultimately ending up together.