Every time I see a three legged dog I call him Lucky.
One Christmas morning about 10 years ago we heard our two Labs making a fuss. I went to see what the problem was and there, in the -5 degree Christmas morning, standing in about a foot of snow was a three-legged Golden Retriever.
I brought him up on the porch, gave him dog buscuits when he inhaled and called the cops with his tag number. They ran the tag and gave me an address about 1/2 mile away. I walked him home and he hopped a bit but made good time. When I got him to his house, his owners, a couple in their late 70's perhaps, welcomed "Luke" home. I asked "Luke?"
"Well" said the man, "It's actually Lucky but we changed it when he lost his leg"