Interesting. I don't think I'm schizophrenic but I'll often "hear" in my head a good rhyme to what I'm saying that doesn't make sense in context but would sound neat so I'll say it - mostly in conversation with people I know very well - primarily to my wife.

It's not uncontrolled, but I do it without even thinking. In normal conversation I've got a part of my brain monitoring and thinking "no don't say that, you'll look weird"