Do rice krispie treats need to be refrigerated, or can they be stored at room temperature? I'd like to know both whether leaving them out is safe, and whether refrigeration will affect their flavor and/or texture.
I don't know about the safety standpoint, but from a texture standpoint -- don't refrigerate them.
The problem is that they turn into an brick when cold -- rather than being a nice dessert, it's something that you have to gnaw at and fear that you're going to chip a tooth.
You might be able to get around this by warming them back up before serving, but I'm not sure what the best way to do that would be. (microwave? low oven?)
So from someone that has been making Rice Krispies Squares his whole life (Grandma taught me) Let's look at your typical ingredients:
Rice Krispies: Does not need to be refrigerated
Marshmallows: If form the bag they do not need to be refrigerated
Butter: Does not need to be refrigerated
Vanilla Extract: Does not need to be refrigerated
So based on that alone should tell you that they do not "have" to be refrigerated. But with everything there is always personal preference.
Gooey, moist, squares: Leave them at room temperature
Firm, Harder Squares: Cool them
One thing to keep in mid though is to always cover them in either situation. If you refrigerate them and they are not covered they will go rock hard and dusty. If you leave them out uncovered for too long you can get the opposite, soggy squares with no snap crackle pop left in them as they absorb moisture from the air.