There was the time DD1 decided to 'make porridge' by pouring a full box of oats on the carpet and then pouring milk on the top. Luckily the oats soaked up the milk so it didn't go on the carpet much.
DD2 likes to pull wipes out the container - once she got through 2 containers before i realised.
DD2 poured 3 litres of milk in the kitchen recently (making herself a bottle) - i have bought fridge locks now.
DD2 has also drawn over nearly every wall in the house. I would confiscate pencils etc only to discover her with one a week later (she had a hidden stash ).
DD1 has also got into vegemite and sudocrem and spread those everywhere.