The tiny brown mouse of the "Tom and Jerry" franchise. While most of the Jerry either outwits Tom, or have others handle the tux-cat for him, there are a few times in which the tiny mouse is able to over power the cat in pure strength.
"Dr. Jekyll and Mr. Mouse"
After Jerry drinking up all of Tom's milk, the cat plots his revenge by making a bowl of milk filled with various posions... and as Jerry drinks it, he dies... only to get back up and becoming a buff unstoppable mouse.
The Tom and Jerry Comedy Show
In the short "The Incredible Shrinking Mouse" a chase between Tom and Jerry leads them to the castle of an inventor. Jerry gets a hold of one them, a grow/shrink ray, and used it to shrink Tom to be even smaller than Jerry, but then accidentally makes him grow even bigger than he original was, making him more muscular/obese. While having that advantage on the mouse, it was short lived; as Tom did the same to Jerry who greatly out grew the cat.
Tom and Jerry Kids Show
A typical Tom and Jerry chase lead the 2 witch's manor. Tom is hired to chase Jerry for the wtich. Jerry finds some monster formula and torunces Tom multiple time.