I've actually became lucid a couple of times because I would be taking a piss in a dream and I would suddenly be like "oh my god I just went to sleep I probably just pee'd the bed!" and I swear I would actually feel warm liquid running down my leg, so I would force myself awake and the feeling of warm pee would literally fade away because it didn't actually happen.

But it is possible because people have told me about peeing in dreams then in real life too.