In the second episode, chain of custody rules over a case of attempted rape which was foiled by the victim biting her attacker's penis off leads to the immortal line:
Meredith What am I supposed to do with a penis?
In episode 9 of the first season, George contracts Syphilis and undergoes a Humiliation Conga resulting in Meredith giving him a Penicillin injection in his butt with Cristina and Izzy watching to their very great amusement. The best part was when the infection was traced, resulting in George attacking Alex screaming:
In season 3 episode 2, Christina meets Burke's parents while she's straddling him in her underwear.
In the season 7 episode "That's Me Trying", Owen puts the residents through a trauma certification drill, instructing them that they have to keep as many of their dummy patients "alive" as possible and that a "rescue helicopter" will be along in nine minutes. As hours go by with no imaginary helicopter, it becomes clear that this was an Unwinnable Training Simulation. But when April and her group are down to their last two dummies, she flips out and refuses to give up, first claiming that she can hear the helicopter, then stealing a nearby ambulance (which was supposedly "wrecked" due to being part of the accident) and driving them round to the front of the hospital. Owen has to tell her they won to snap her out of it.
Anyone want to argue with my extra special vagina vote?
In season 7, during Cristina's BSOD arc, she temporarily begins working as a bartender, to hilarious results. Seriously, one of the FUNNIEST episodes this troper has ever seen.
In the Backdoor Pilot for Private Practice, Addison's lampshading of the status of elevators in Grey's Anatomy— first the long monologue about how nice it is to be somewhere where the elevators aren't aphrodisiacs (to a man she's never met), followed by her conversations with the "Elevator Gods". It's made much more hilarious because it is such a lampshade.