These are the direct result of random firings of neurons in the language center of your brain. Your inner monologue will suddenly begin spouting random words into your consciousness. Some may have no meaning:
Dr. Pepper halogen Donna Pescow
Sometimes, through sheer randomness, the vagrant thought will make a certain kind of sense, forming a complete sentence or thought:
When dogs run over mushrooms, asphalt will melt into a raspberry flavored sauce that tastes good on chopped rutabagas.
Still other times, the vagrancy may form a question, one that you probably should Ask Jeeves about:
Where can I find fat women with big boobies who are waiting ... just WAITING ... to treat me like trash?
Usually, the speech center of the brain is very judicious in preventing these vagrancies from actually being vocalized. Sometimes, though, a vagrant thought will escape, usually resulting in, at best, mild embarrassment, and, at worst, commitment to a mental institution. No further examples will be provided, to protect the gentle sensibilities of just about everyone.