You probably played with them all the time.
It’s perler beads. Except you probably ironed them into… the shape of a duck, if their website is to be trusted (I ironed mine into the shape of a blob, that was the shape I was intentionally going for) and Sabine Ducasse ironed them into an entire cool outfit. To be fair, she is probably an adult! She has better ironing skills tan you did at the time! But, goodness gracious, look at how beautiful and wearable this is. Would you wear this? I would almost certainly wear this. I suppose it might be tough to bend in, though: