Throughout the series, Leonard has run-ins with different study group members that usually lead to an exchange of insults. The format is that Leonard barges in on a conversation with an insult or irrelevant information and then somebody retorts with a cutting remark. It originally involved only Leonard and Jeff but Shirley and Britta have each gotten a "Shut up, Leonard!". This running gag's first occurrance was in the Season One episode "Advanced Criminal Law".
|“||Oh, come on Leonard. If you're going to argue with me, put on a bathing suit.||”|
–Jeff, Advanced Criminal Law
|“||Shut up, Leonard! Nobody even knows what you're talking about!||”|
–Jeff, Romantic Expressionism
|“||Shut up, Leonard! I talked to your son on Family Day. I know all about your gambling.||”|
–Jeff, Physical Education
|“||Shut up, Leonard! I heard about your prescription socks.||”|
–Jeff, Biology 101
|“||Shut up, Leonard! You smell like mentholyptus. What are you even doing here?||”|
|“||Shut up, Leonard! I found your YouTube page. What's the point in reviewing frozen pizza?||”|
–Shirley, Foosball and Nocturnal Vigilantism
|“||Shut up, Leonard! Those teenage girls you play ping pong with are doing it ironically.||”|
|“||Shut up, Leonard! I know about your crooked wang.||”|
–Britta, Introduction to Finality
The running gag is also subverted once when Jeff is under the influence of anti-anxiety medication:
|“||Looking good, Winger.||”|
|“||Thank you, Leonard. For that compliment, and for your service to this country.||”|
|“||Shut up, Leonard! I got a picture of your old nose, it was a lateral move!||”|
–Dean Pelton, Basic Human Anatomy
|“||I told you you'd be back.||”|
– Leonard , "Repilot"
|“||Shut up, Leonard! I'm not here! I'm just a figment of your creeping dementia!||”|
–Dean Pelton, "Repilot"