The Big Bang Theory Season 4 Episode 13
The Love Car Displacement
Amy convinces Penny to come with her to a science seminar once Penny learns it's at a spa.
After meeting Bernadette's ex-boyfriend (Rick Fox) Howard started to feel inadequate and said some things that hurt Bernadette's feelings.
The gang played revolving roommates as each had difficulty getting on with their respective bunk partners.
Penny and Leonard started to have sex, but were interrupted by Raj whom Sheldon had banished from his own room.
At the panel, Bernadette and Howard exchanged euphemism-laden barbs at one another over Howard's feelings of inadequacy. Amy pointed out they were talking about penises, and Raj concurred, while Penny just wanted to get the hell out of dodge, prompting Bernie's ex-boyfriend to offer her a ride back to LA - much to Leonard's chagrin.