DD absolutely does this. For her it's because she has an obsession with finding things that are funny and it's a way of testing out humor.
I will say, though, that once she started preschool she started neglecting certain activities more. I think a big part of it is that she's an extremely social kid and was very focused on the social aspect (and this was shown too because she really wanted to do pretend play, barbies, etc). Sometimes she'll purposely make mistakes and I think it's more to get us to participate in whatever she's doing (counting, spelling etc) because she really wants social interaction at all times.
