You have to pick:

My dog licks my face for a long time whenever she gets the chance - how's this different?

Human mouths are significantly more disgusting than dog mouths.

You don't have to pause to think of the rhyme, it just happens automatically (it's a brain thing).

Joke's on them, I've got a cold right now.

I would love to be able to rhyme all the time without thinking about it.

I assume this only happens once?

Yeah.