10+++ years ago, we used to play with this kinda stuff at a
friend's house.
i've no idea if they will come off or not 
we never asked and she never said anything.......
=\
we also played with 'invisible ink' pens.
i remember drawing stick figures with those....
on the walls in her room.....
she drew pooh
(the bear)
and then we made up stories in the dark about pooh and the stick
figures....