Season 5, Episode 12: Jacked
Funny thing that happened on this one: Larry and Alan get into a debate about something, each conceded the other's viewpoint, and they resumed arguing on opposite sides of the debate.
Did you know that Orville and Wilbur Wright did the exact same thing? I once made a visit to The Henry Ford Museum's Greenfield Village in Dearborn, MI with my son's school field trip and spoke to the tour guide who told me how fascinating the arguments between the brothers were.
http://en.wikipedia.org/wiki/The_Henry_Ford#Greenfield_Village