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1.
Rodents of Unusual Size, from the 1987 movie, The Princess Bride. They are known to attack in the Fire Swamp.
-After Westley rescues her from the lightning quicksand-

Buttercup: We'll never succeed. We may as well die here.

Westley: No, no. We have already succeeded. I mean, what are the three terrors of the Fire Swamp? One, the flame spurt - no problem. There's a popping sound preceding each; we can avoid that. Two, the lightning sand, which you were clever enough to discover what that looks like, so in the future we can avoid that too.

Buttercup: Westley, what about the R.O.U.S.'s?

Westley: Rodents Of Unusual Size? I don't think they exist.

-Immediately, an R.O.U.S. attacks him-
by Kaarmu June 01, 2007
 
2.
Rodents Of Unusual Size. These guys seem t be a higher level Lab Rat in Borderlands.

They also have adapted an unusual power to shoot a type of shock beam with their now goggle'd eyes.
When my friend and I are going through on level 50, we see these futuristic larger rat type enemy. They are called R.O.U.S.; short for Rodents Of Unusual Size
But when we are boosting lower levels with our level 50, we only see Lab Rats.
by EpicAurbis November 06, 2012