I once worked in a store that had a "shop cat". We got him when he was around 6 months old.
He was freakishly long, had huge paws & flaps of skin from his legs to his body (think flying squirrel). Boy did he grow into all that. In his prime he was 25 pounds and at that point, not a bit of fatness.
When he was older, it was more fat than muscle.
This is a not so good quality picture of me holding Sisko. Not sure if you can see his true size, but consider I'm 6 foot long myself.
For me, he was the original "damn good cat".