What was the first TV show to have a toilet tank shown on prime-time TV?

As a 1950s television sitcom, Leave It to Beaver was the first TV show to feature a toilet tank in a scene. In fact, this show had a unique history. It had an extraordinary number of bathroom scenes. Moreover, Beaver and Wally Cleaver as brothers had an en-suite bathroom. Many scenes on the show were set in their room.

One of the first episodes, "Child Care" is set almost entirely in the bathroom of Wally and Beaver. Other episodes also include major scenes set in the boys' bathroom. Additionally, in almost every scene set in the boys' bedroom, the bathtub, shower curtain, or vanity can be seen through the open bathroom door.

Beaver uses the bathroom several times to escape his brother when angry, slamming the door to express his emotions. At such times, June and Ward, the boys' parents, are called upon to order Beaver to vacate his refuge. In "Beaver's Good Deed", a scene is set in Ward and June's bathroom. A tramp takes a bath in their tub and slips away wearing one of Ward's suits and a pair of his shoes. In the "Captain Jack" episode, Wally and Beaver try to hide a baby alligator they bought by keeping it totally in the toilet tank in their bathroom. This tank was in fact referred to as Captain Jack's "aquarium" by Wally. The boys had kindheartedly named their alligator Captain Jack after he had been purchased.