Though his penis was so large, it did not grow when he had erections - it merely became firmer.
In fact, the first known mention of the bubbling phenomenon was mentioned in Vice by Australian skater Troy West, who says that the practice is so common in Australia that it's passed on from generation to generation like a precious heirloom.
It began with a picture of a young man at a rock concert; a young man I assume so overtaken with the music he was listening to that he had no choice but to whip out his garden hose and start peeing into his own mouth as a self-soothing strategy for all the feelings he was experiencing.