All four of my children have had this divine obsession with the toilet. They would constantly be wandering in to pay homage to their “Porcelain God.” They would perform splashing rituals, getting themselves and the entire bathroom soaked. They would offer sacrifices of toys, cooking utensils, and iTouches. (Apparently they wanted to be sure I was also in good favor with the Almighty.) Cleaning rituals were of utmost importance as well. On more than one occasion, I found myself with a toilet snake, boring out a brand new bar of soap that had been stuffed deep into the pipes. For weeks the smell of aloe and springtime wafted up from the depths of the throne.
So what can a mother do to deter the worship of this false idol? One idea is to super-glue strong Velcro to the seat and the top of the toilet. Get the kind found in hardware stores, not the weaker kind found at craft supply stores. The problem with this idea is two-fold: 1) The Velcro is not very comfortable to sit on, and may cause a rash in the most unfortunate of places. 2) Getting the Velcro off once the children have grown out of this phase is not going to be easy. Buying a new toilet might be a better option at this point.
Another idea might be to place a heavy object onto the top of the toilet seat, but there is danger of said heavy object crushing the little toes of a determined worshiper. It might also make emergencies more, well, emergent! Keeping the bathroom door closed might work out best as long as the rest of the family can be counted upon to follow through. (Good luck with that one.)
Alas, the best and only real option is patience and constant reminders that the toilet is actually evil, and must be avoided without parental support. Also, make sure you are prepared with a plunger and a toilet snake. They come in very handy, and are much cheaper than constant calls to the plumber.