It wasn't too long ago that you could collect all sorts of wonderful items from boxes of breakfast cereal, usually found amongst the cereal itself, these free toys etc were probably one of the selling points of which cereal to buy, it certainly was for me. Now there is very rarely anything much you get free except maybe a free book or an offer of some sort. Why did they stop doing these free toys etc? Probably something to do with health and safety.
Anyway here is the front and back of a Shreddies box which came out during the 1990's in which inside each box contained a free plastic spooky spoon which would change colour when put into a hot or cold drink. There was Ghoulish Green which when put into a hot drink would change into Molten Yellow. The Green spoons were Frankenstein and Cyclops. The last two to collect were the Blood-Curdling Blue spoons which turn Spine-Chilling Purple when put into a cold drink. The Blue spoons were Dracula and Skeleton. These were a nice novelty and nice artwork on the back of the box. I used to have all 4 of the Spooky Spoons but I lost one somehow, I'll put the 3 I have on sometime.