My 8 month old (as yet) un neutered Labrador takes great delight in stealing things and doing a runner. He thinks it's hilarious to be chased. If I ignore him he soon settles down to gnaw on whatever he has taken and ingesting pants/plastic/toys/ gravel which I know can't be good for him.
Tonight he managed to grab a piece of lolly wrapper from the lolly I was unwrapping for DD aged 6. In the ensuing chase, he managed to knock her flying into a display cabinet, I eventually managed to corner him and retrieve the wrapper, shouted at him in my harshest voice 'you naughty boy' and sent him in disgrace to his bed.
If I chase him it's a game, if I don't he risks making himself ill, I really don't know how to deal with this!