I tried doing this myself, and you can read about it here). According to the advertising, Lucky Charms contains marshmallows, so therefore some might consider Circus Peanuts to be marshmallows.
It's a difficult thing to really nail down, but recently I was inspired. I thought the best way to find out if Circus Peanuts are in fact marshmallows is to compare them physically. Sure I could do some science like stuff and compare the ingredients, but I have a better idea. Why not try and find out if Circus Peanuts act like marshmallows. After all if it has feathers and quacks, then it's a duck.
For my first experiment I've decided to see if Circus Peanuts work in a recipe that's tied closely with marshmallows, Rice Krispie Treats. I'm going to make two batches of Rice Krispie Treats, one with normal fresh marshmallows, and one with an equal amount (in weight) of Circus Peanuts.
The thing is, the Circus Peanuts did eventually melt, but I'm not certain it's because of a gelatin breaking down in the heat, I'm thinking it has more to do with the sugar melting. This means that if you're trying this experiment at home yourself, keep an eye on your Circus Peanuts because if it's the sugar melting than it's likely going to burn fairly quickly.
Putting the marshmallow Rice Krispie Treats into a pan is sticky, but fairly easy (particularly if you're liberal with the butter). The Circus Peanuts were a bit more challenging, but manageable. I should mention that I was really surprised that the Circus Peanuts worked this well, I thought they wouldn't make it our of the pot. I eventually managed to flatten both batches of Rice Krispie Treats, however the marshmallow ones looked much more blended.
Flavour wise I was pretty happy with both treats. I've always loved Rice Krispie Treats made with marshmallows, in fact they're my favourite way to eat marshmallows. The Circus Peanut Rice Krispie Treats were not bad either. The cereal gave the normally strange texture of the Circus Peanuts a bit of a crunch, which is good. It also killed the flavour of the Circus Peanuts a bit, and that's not a bad thing either.