"We're fire fighters! We fight fire."
"Yeah, and I fight fire with fire!"
"...That just makes more fire."
I love TomSka's sketches, I really do. I will say that I've long outgrown the asdf series- its randomness generally meant the absence of a decent joke aside from "Wow, that was weird"- but all of his sketches are able to explore a scenario fully fleshed-out very quickly. Fire Man is probably a prime example, clocking in at just over a minute.
The whole premise is deliberately and delightfully corny: Fire Man, a superhero who shoots fire out of his hands, is being let go as his powers contradict with his occupation as a fireman. He quickly suspects it has to do with the hiring of Water Man, a prickly, self-amused superhero who he grows to hate with a fiery passion (Get it?). Sure, the latter is a unnecessary joke, and the idea that his powers to shoot water are controlled by the amount of urine in his bladder is a bit overdone, but it helps round off the sketch and keep it moving along quickly.
One of the things I like the most is the sheer normalization of the situation. Fire Man isn't portrayed as stereotypically heroic so much as a normal person, which I appreciate. Tom's delivery nicely underplays the hokey premise to make it light, but again, well-explored, which really helps, even if the ending jumps off the deep-end. Even then, though, it's hard to complain considering that seems to be the easiest way to end a sketch without letting it run dry too quickly, so it's not an issue so much as a minor complaint.