Part of the problem might also be that not everywhere pronounces cot the same. See the cot-caught merger. I’m from a part of the US where cot and caught are still pronounced differently and I pronounce twat like cot, both with a short a sound.
I don’t think the cot/caught merger would be a problem, though I suppose it’s not impossible that in places in the US with the merger, the word in question always rhymes with cat.
Part of the problem might also be that not everywhere pronounces cot the same. See the cot-caught merger. I’m from a part of the US where cot and caught are still pronounced differently and I pronounce twat like cot, both with a short a sound.
What’s the joke?
I don’t think the cot/caught merger would be a problem, though I suppose it’s not impossible that in places in the US with the merger, the word in question always rhymes with cat.
As for the joke, one telling can be found here: A dwarf and a horse