Poppin’ Hoppies were little mushroom-shaped plastic toys with spring-loaded stalks.
Employing large amounts of saliva and spit, you pressed their heads down to the base where they stuck temporarily due to aforementioned saliva.
Suddenly – when the suction cup dried sufficiently – they sprang into the air with a big pop.
And that was it.
Considered quite high-tech at the time, the little buggers would never all stay scrunched up at the same time for the game to start, so you had to have everyone that was playing leaning on a couple of them each until they were all set.