Clark: Lana. What are you doing down here? Lana: Probably the same thing you are. It's peaceful. Clark: You're 2 for 2. You keep showing up when I least expect to see you. Lana: I'm not trying to surprise you, Clark.
The expression comes from sports, or maybe betting. It just means to have played twice and won twice: "Will she be able to go two for two in the match this afternoon?" means she's already won once, and if she wins again, she'll be two for two. She might be going "three for three" or "two for three" or lots of other combinations.
So, I'm guessing Clark has run into Lana once before, and