Most of these we learned as a parent, some of them we knew but they were reinforced... in a negative way.
1) Children don't need cute little busy books. If you want to entertain them with a book... get them the Toys R Us Christmas catalog and just sit back and listen to "I want that and that and that and that and that and...."
2) Words most often heard from your child around Christmas time... "I want that and that and that and that and...."
3) Just because a crayon/marker says 'washable' does not mean it is 'washable' on ALL surfaces.
4) Highlighters, ink, and tubby/bathroom crayons will NOT come off of walls. No product on Earth (not even bleach) will get it off the wall. The best you can get is a bit of fading.
5) Tubby crayons are not safe on all surfaces in a bathroom. They will clean off of mirrors, tile, ceramic, and laminate. It will NOT clean off of porcelain. We have a toilet seat to prove it.
6) Crayons are wax and will melt in hot cars. Your car does not need to be very hot for this to happen and it will not melt, just a little bit. The entire thing will melt and run all over your car and be a real pain to try and get it off the upholstery.
7) No matter what you do at your job, your toddler will think when you go away to work, that you are actually just having recess all day and eating snacks. And therefore, your job is better than daycare/school.
8) If you won't let them do something or buy a certain something for them, you can bet that they have a friend that gets to do that same thing or that friend's mom has bought that certain something. And therefore it completely validates their reasoning
9) When you ask a toddler why they did something their first response is always "Because". When they are older it's always "because ______", which totally validates their actions and absolves them from consequences and responsibility.
10) If you cannot see them do something, they then did not do it. So, kids will go to another room or out of eyesight just to do something they aren't supposed to, because they feel they can plead innocence.