I've been a bit naughty.
I have an Amazon wishlist for the boys that my mum buys off. When I add things to it I write in the comments who they are for. Ds3 and 4 wanted these Goo Jit Zu things, but ds3 specifically wanted the white and ds4 wanted the red. I noticed that she hasn't bought the red one, and was finished shopping so I bought the red one. We exchanged gifts today and I was sorting them to go under the tree just now and recognised the shape and feel of a Goo Jit Zu in ds4s bag, and not in ds3s. I very carefully peeled open a corner and she has accidentally given the white one to ds4. I know that this will be a big issue between them.... so, I found the red one that was from Santa, switched the tags and put both Goo Jit Zu's in to the right bags, so that's one less from Santa for ds4, but they now both have the right colour one from Nanny and no one but me need ever know.