Scratch and sniff
Scratch and sniff refers to paper that produces an odor when it is scratched. Scratch and sniff is mostly used on stickers. Scratch and sniff stickers are frequently given to children as a reward for doing well in school.
Scratch and sniff is created by covering the odor in a covering that breaks easily when it is scratched. Because the odor is covered, it can be kept for a very long time.