An unpleasant surprise

I would mix the meals around in the fridge, so that person would be in for the bad day.

Why would you leave a note? Surely you'd want them to eat it and be like "OH SWEET LORDY!" and then later tell them it was you

I actually did this once. My Mother died. Before she was even cold, the relatives were pulling out here will, and deciding who gets what. My Mother and I had food storage (a year's worth) and they were eating it ALL. They polished off 3 months worth in 5 days! My Mother kept a stack of 'blackberry cobblers' (aka pie) in the freezer and they were eating 2 a day. So one day I crushed up some laxatives and sprinkled them over the cobbler. Their greedy assess didn't see that one coming.

If you don't put the warning then it is considered poisoning someone, even if they are stealing your food to do it (-_-) Just like the people who break into a house to steal, get hurt, then sue the owner. Stupid. Very very stupid. But it is unfortunately how things work.

Problem solved

I would make ALL of them with laxatives... while taking the toilet paper from the bathrooms after lunch.

As someone who uses them, that is not how they work. It takes 6/12 hours for them to kick in. You need some powerful stuff in order for them to work right away.