Any toilet seat that does this bullshit. Sitting there and suddenly it feels like the

They’re basically little brackets that you secure to the underside of the toilet seat and are usually roughly “L” shaped. The stick on ones are generally crap unless you’re a pixie that sits like a statue. Spoiler: if you need these things you aren’t that person likely. So get the screw in stops not the tape on ones. You’ll need to drill a hole into but NOT THROUGH the seat and screw these in. Two brackets, one on opposite sides of the seat from each other. One flat of the “L” goes on the seat and screws in, the their side of the “L” hooks down into the bowl on the lip and stops the side to side movement that loosens seats.

If you only have a very mild and occasional problem with this and don’t feel like buying things or installing them (both products are cheap FYI. Usually $5 or less each,) but if that’s too much money or effort... not “flopping” onto the seat helps a lot. As does not wiggling your butt on the seat. You’ll say you don’t flop or wiggle. Yeah. Every person I’ve done brakes for after only a few months since the last new pads has also sworn they “don’t ride the brakes.” Well... someone is, and if they stop- the problem will likely stop too. But- those are the major options that aren’t too extreme like specially designed hardware or new fixtures. $10 or less and you can essentially never have a wiggly seat again! For free you can just tighten it every week or whatever schedule it seems to loosen at and you’ll not sit down and have it be crazy wobbly.

Just fix it for them and don’t say anything. With no tools and strong hands it can be done in 5-10 minutes. If you have a small screwdriver or any flat object that can work (like a butter knife etc,) you’re in business. If you buy a tightening kit for like $5 it will come with the tool for the nuts so you don’t have to use your hands if they aren’t strong enough. Lefty (counter clockwise) on the nut to loosen, righty (clockwise on the nut) to tighten. Hold the “screw” in place, no need to turn- just turn the nut until it is tight.

Assuming like 99% of toilets the hardware is nylon/plastic, you can’t really do any damage to the toilet unless you really tried. Simple, fast, easy, and they never have to know if you do t want them too. If they find out or figure out it was you- you just BAM! Tell them it was a surprise out of love and play it off.