1. In some South American countries where small rodens are common, people struggle to differenciate between a mouse and a rat, so they use the name "RattyMouse" to describe both.
2. The description of a loveable partner or friend that has rodent like feature.
Jose: Damn man, who ate the rest of my chicken I saved last night, I was going to have it for breakfast?
Enrique: It wasn't me amigo, I saw a "RattyMouse" eating it last night, but I was too drunk on tequilla to do anything.
Jose: You drunk fool! Now I will be hungry all day because I didn't get my breakfast. It's your fault.
Enrique: I hate you!
This is what LADS say when they can't swear and say "Dumb Motherfucking Bitch" as both the school and the parents don't allow children to swear...
"Stop stealing my toys you Diddle tootie footie ritty booty motherlicker!!!"
Or
"That Diddle tootie footie ritty booty motherlicker is the worst guy I have ever seen..."