There was a shepherd, and his sheepdog died.
One of the rams said to the shepherd, "Shave my wool and cut off my horns, and then put the sheepdog's skin on me. The wolves will see me and run away!"
The ram's plan worked: when the wolves came, they saw the sheepdog, or so they thought, and ran.
One day, however, the ram was feeling very bold, so he chased the wolves and, as he ran, a thorn snagged the sheepdog's skin, leaving the ram naked and defenseless.
No longer afraid, the wolves turned on the ram and devoured him.
Inspired by: Mille Fabulae et Una, a collection of Latin fables that I've edited, free to read online. I am not translating the Latin here; instead, I am just telling a 100-word version of the fable.
Notes: This is fable 313 in the book, which is Perry 705.