When House said Everybody Lies, Gabe was the first to point out the logical paradox in the statement - the statement had to be a lie. House countered that the rule wan't that everyone lied all the time, just that everyone does it at least sometimes.
Gabe also asked what House did all day if he only had one patient. House tells them about having a fight with Cuddy.
Gabe then wondered how Taub could be good looking if he was short and had a big nose and when House intimated that Taub also had a big penis, Gabe accused him of lying again. He later accuses House of lying about the stories about the patient coughing up a lung and stealing Cuddy's laptop. His teacher admonishes Gabe about calling people a liar, but Gabe counters that House already did so. However, later on, Gabe is convinced House is telling the truth about the patient's lung and about convincing the patient's roommate to hack into Cuddy's computer.