I have a huge cat. She is about 35 lbs.
Before anybody gets upset with me -- let me explain. She is turning 7 this month. Since she was about 5 weeks old (when I first rescued her off a farm where her momcat disappeared -- some of you know the story) she has NEVER been a normal-sized cat. I want to think she's a cross-breed between a cat and some larger variety of cat! But unfortunately I don't think that's true, because she IS fat on top of being large-boned! I've had her at vet after vet after vet, and no amount of vet-prescribed meds or diets have changed her weight whatsoever. She is still on her diet.
Having said all that, I checked into GWR and was planning to submit an app for the largest domestic cat (I think I would have lost - I think I saw something larger, closer to 40 lbs) but they said they no longer accept apps for the "largest" or "smallest" animal because they think owners over-feed or under-feed in order to make records. I totally understand that and respect that, completely. So my cat is not in the GWB.
I think some of you have seen my infamous cat-in-sink photo. This is when she was NINE months old. Already overflowing the sink.
I should be grateful, and I am, that my other 4 cats do NOT follow in her footsteps.