Very nice, it didn't stray too far from the real show (somehow I wouldn't put 'that' past Toph :P) And it was pretty cool with the implied pooping (I think my bending poop comment from way back has created a trend XP).

Good luck with this, can't wait to see more stories in the contest.

This is pretty good for a brief, funny story, but I see problems with it. The most obvious is that it jumps back and forth between past and present tense. Another problem is that I find it hard to believe that, in the space of time that Toph is in the bathroom, Katara's need to pee goes from the first twinge to being so bad that she, a high school-aged girl, uncontrollably wets herself. I can't imagine that taking any less than 2 hours, unless Katara drank tons and tons of liquid for some reason. I think you should have done 1 of the following:

A. Make Katara have to pee at the beginning, but ignore it until Toph goes to the bathroom, since she knows Toph will be in there forever.

B. Have Toph stay in the bathroom for a *very* long time.

C. Provide some reason for Katara having lots of liquid in her system.

Moving to the positive attributes, I love the "I gotta go move some earth."/"I really didn't need to know that" part. I also like the bending part, especially her "pulling" it out of her bladder, hurting herself, but I wish that part was longer. I also wish you hadn't written in the part with Toph playing with herself and Katara getting excited from it, since I never like reading about that stuff. The end is a real plus. *Not* seeing the scene with Katara throwing pee at Toph is probably even more fun than seeing it. I think you ended it at just the right time.