I think we should all hope that, someday, science will allow us to go to parties where we change our genders and sexuality and then act prudish and uncomfortable as all hell about the situation.
The whole pizza man thing makes no sense. Why wouldn't he assume that Tedd had a sister? Why would he immediately think "Oh, hey. That's Tedd. Crossdressing. With fake breasts."?
Oh. Whoops. That wasn't AHR. That was Cakman. And this is Cakman too.
This, however, is Myrmidon. And nothing can prove otherwise.
"What does this contribute to the plot?" You'll never appreciate El Goonish Shive with THAT atttude. I don't really care about the plot - usually - but I enjoy the comic for its humor.