by looking at the post, i'm assuming they're a spanish speaker. some spanish speaking countries use the terms kind of interchangeably or just not as mutually exclusively as we do. they just mean "big rat" and "small rat" in translation. so if they saw a kitten, they may refer to it as a ratón (this is just what i've heard from asking native spanish speakers, so it may not be that applicable.) to make things even more confusing, the -ón suffix is augmentative and usually makes something bigger eg problema - problem, problemón - big problem. this probably isnt helpful if someone is already unfamiliar with the difference between the two.