She's smug about how the "sky cells" break everybody. So Tyrion launches into a long list of his crimes, which include lying, cheating, gambling, and whoring. He has an anecdote about a servant girl's bouncy breasts. Then he launches into a story that contains the following euphemisms for masturbation: "milking the eel," "flogging the one-eyed snake," "skinning the sausage," and "making the bald man cry." All of which he did into some turtle stew, which Cersei then ate. He then launches into a story about bringing a jackass into a brothel, but Lysa cuts him off. Robyn would like to hear the rest of the story (because it was probably going to be pretty entertaining), but that is not to be. The only other person who seemed to be enjoying Tyrion's stories was Bronn, the sellsword who helped Catelyn drag Tyrion here. I mostly mention that because I looked up his name and want to start calling him "Bronn" right away.
Lysa reminds Tyrion that the crimes she's interested in are the murder of Jon Arryn and the attempted murder of Bran Stark. Tyrion says he didn't do either of those things, and then orates about justice and getting a fair trial. Lysa thinks a trial sounds delightful, because if Tyrion's found guilty, he gets the Moon Door, which is a big hole in the floor that reveals that there's nothing underneath the throne room. It just drops straight down thousands of feet. I'm not sure it's a good idea to have one of those in the middle of the floor like that. Anyway, Lysa figures that since Robyn's the one who's going to deliver the verdict, the trial will be pretty short. But Tyrion has a twist for her! He wants a trial by combat. Which is something they apparently have here. Lysa is immediately inundated by armored gentlemen who just can't wait to kill Tyrion for her. Robyn shouts, "MAKE THE BAD MAN FLY!" but I'm not convinced that he hates Tyrion so much as he just likes seeing people dropped through the Moon Door. She picks a knight who was almost the only one in the room who wasn't waving his hand yelling "Me! Pick me! I wanna do it!" The knight points out that there isn't a great deal of glory in killing someone half his size, but that's okay. Because Tyrion would also like a champion to fight for him. Specifically, his brother Jaime, who can probably be here in a week or so. This proposal is rejected by Lysa, who says that the trial has to be today. Oh, right, Tyrion's been stuck in the Sky Cell for untold weeks, but now we're on a schedule? Tyrion asks the room if there's a volunteer to fight for him. Everyone laughs. But then Bronn steps forward, saying, "I'll fight for the dwarf."