A difficult question or problem.
Season 2, Episode 10 - The Vartabedian Conundrum
Aired December 8, 2008
After Leonard comes to the realization that Stephanie has moved into his apartment, he begins to feel their relationship is progressing too quickly for him. Leonard turns to Penny for advice on how to slow down his relationship. Meanwhile, Sheldon requires Stephanie's medical attention when he's convinced he has a mystery illness.
Season 7, Episode 14 - The Convention Conundrum
Aired January 30, 2014
When the guys don't manage to get Comic-Con tickets, Sheldon plans to hold his own convention and ends up spending a memorable night with James Earl Jones. Meanwhile, Leonard, Howard and Raj consider buying scalped tickets, the girls try to act like "grown-ups".
Season 10, Episode 17 - The Comic-Con Conundrum
Aired February 23, 2017
After turning down his father's money in a bid to more self reliant, a cash-strapped Raj puts Sheldon in charge of his finances. When Sheldon imposes financial discipline on Raj, he is disappointed to learn that he might not be able to afford to attend Comic-Con this year.
Meanwhile, Penny decides to join Leonard at Comic-Con this year, while Bernadette makes Howard work harder around the house if he wants permission to attend the convention.