Like many families, we ate a lot of cereal when we were kids. My mother almost always bought the “healthy” cereals like Cheerios, Rice Chex, or Raisin Bran. These cereals weren’t typically marketed to children (more to adults with buzzwords like heart disease prevention, etc.), so I think we were generally unaware of a lot of the kid-directed promotions you’d see on the sugary cereal boxes. I do remember that you could collect box tops to mail away for free stuff. Is that still a thing? Asking for a friend.
The only toy I remember saving box tops for was a talking Chikorita spoon from Kellogg’s circa 2002 or 2003. For the uninitiated, Chikorita is a Pokemon. My brother got Pikachu, I think. The idea was the spoons said their name when you dipped them into the milk. They didn’t exactly work, but it was just as well, since my brother was allergic to milk and ate his cereal dry.
A much bigger cereal box success was the 1996 Rice Chex promotion: a free CD-ROM of Chex Quest, a ridiculously fun first person shooter. Chex Quest was essentially a re-skinned DOOM, but we didn’t know that and loved it. My parents didn’t mind that it was a shooter, because it was considered “non-violent”: you’re technically transporting the Flemoids with a transporter gun, not killing them. The fact that the sound effects were weird and thoroughly enjoyable to imitate over and over around parents was a significant perk as well. We played Chex Quest and the later sequel, Chex Quest 2, over and over again. Here’s an embedded video of gameplay – enjoy!