I believe the first on-screen toilet was on Leave It To Beaver. I think Wally and the Beave kept a pet turtle in the toilet’s tank.
Remember all the work Wally and the Beav put in to fake taking a bath? Wet the washcloth. Dampen the towel. Throw a little turtle dirt in as the tub drains to leave a ring. LOL.
I thought it was a pet alligator.