surprisingly common, in bedrock baby zombies (and husks/drowned) can jump onto their bigger brothers and ride them (ofc ive never seen a baby drowned but still) ive only seen this in hard mode though so im maybe wrong.
ye. if you want any more fact feel free to ask me! im always happy to give you and other members of the community useful (or useless) info and trivia on our favorite blocky pixel game!