I'm attempting to write my first "whodunnit" style novel about a comic book artist who stumbles on a murder during a comic book convention. I introduced a sort of comic-relief sidekick at the beginning of the novel, and one of his running gags was a tendency to make up double entendre based phony names.
Yesterday I was laying out alibis for my suspects, and one of them, an actress of the "she ain't pretty she just looks that way" variety has an alibi in the form of a drunken one night stand. When they ask for the one nighter's name, it turns out to be one of the sidekick's bogus IDs.
I hadn't planned it that way. In fact, I had planned a long distracting search for the alibi, but this little spontaneous bit not only allowed me to dump a blind alley that would have just stretched things out too far in wrong directions, as well as tell the readers that they have to pay attention to the little details.
I think I'm finally getting the hang of this thing, because it's usually something I don't think of until the rewrites.