In which Lance is easily distracted, and Keith is quick to exploit that. So the thing Lance has learned about Keith is that he has a long, long memory. It's selective as hell, but if Keith cares enough about something to notice it in the first place, he'll never forget it. And because it's Keith, he'll usually remember whatever it is at the worst possible time.

Lance likes games. Through a lot of trial and error, this is what Keith has learned: the more random and casual Lance is being, the closer Keith needs to be listening, because it means Lance is trying to tell him something important.