It's been a while since Psy surprised Madonna fans at her Madison Square Garden show to perform a "Gangnam Style"/"Give It 2 Me" mash-up with the sultry songstress. But there's even more to their partnership than what you saw on stage. On an episode of Taxi on tvN, Psy praises Madonna as the most memorable performer he's ever worked with. Psy says, "After seeing me, Madonna told me, ‘On stage you can touch me wherever you want.’” He goes on to say that because she's his senior, he has to do what she wants. Watch the performance here: Who would you love to see Psy collaborate with next? (Source: enewsworld.mnet.com)