Wish I'd known the sticker one! Now that mine are 15 and 11 I no longer need to know.
Did know about the envelope vest thing, but only by the time I'd had DC2.
One that I used to do was to put tights under trousers, used to be extra warmth on cold days for both DD and DS, and was also helpful as DS in particular was prone to whipping his socks off. Couldn't do that with tights. yes, I know some people might say boys don't wear tights, but who's going to know when they can't be seen under the trousers?