What are these cereal freebies called?

I have several small plastic sheets with Flintstones pictures on them. You colour these things with pencils and then put them in the oven for a few minutes. They shrink to form a colourful and neat looking keyring.

Does anyone know if this technology has a specific name?

Sounds like a Shrinky-Dink (but I think I’ve seen them called something else recently – something less memorable).

Shrinkie-Dinks. It’s a brand name, IIRC, but I’ve never seen them called anything else.

AFAIK, all cereal box toys and fast food kid meal toys are referred to as “premiums”…
…nothing premium about over-priced cheap manufacturing…

I’ve also heard them called (not sure of the spelling here --) Shrink-Lits or Shrink-Lets.