The heading illustration suggests Kellogs pack their cereals to suit the country of sale. The UK version had model submarines in which baking-soda would make them dive and rise - as Walter describes.
Also metal puzzles, generally two or three curled pieces of thick wire which appeared inseparable - the secret was to interleave them rather like key-rings. I can't remember who sold them in what cereal.
Much more recently (1980s?) Weetabix packets had cut-out and fold models of the company's delivery-lorries printed on them; but I recall another cereal manufacturer back in the '60s pre-dating that with similar models of animal heads.
