Belladonna's description as written by her player:

Belladonna is, in a word, big. A bit taller than the average mare and much, much larger, Bella is a girl who knows how to eat, and clearly does so often. The whole of her form is thick and rounded, but nowhere is this more apparent than her belly, which stops just short of touching the ground when she stands and often swings about when she walks. Her rear, too, is a masterpiece of soft and ample flesh, the size of it nevertheless making her curious lack of a cutie mark all the more apparent. Her coat is soft, an almost dreary light grey in color and made all the more so by her short, black mane. Her tail is long and swept-out in contrast to her mane, and absentminded Bella seems to knock over more ponies and inanimate objects with it than she'll ever realize. Her size can be intimidating to some taller creatures, and this isn't helped much by her shining, ruby red eyes which, while often bright with an undefeatable levity, are still rather spooky.

In spite of this, Bella's mannerisms make her one of the least threatening ponies one will ever see, which is quite a feat when everyone else around tends to be cheery and brightly colored. Her manner is one of a relaxed, contented happiness punctuated by throes of hunger or passion. She always has a bright smile to spare for passers-by, and is often seen lying upon her side or over her own bloated middle. Her voice is bright, nearly childish in tone, often quoting her grumpy brother on topics for which she knows little. She often has food close at hoof, usually in a leather satchel at her side, and it's not uncommon to see her scarfing down a pastry or two when she has nothing better to do.

Lying against (or upon) Bella is an experience all its own. If you can imagine the softest, most overstuffed sofa imaginable, complete with its own internal warmth, you've got a fairly good idea of what Bella's middle is like. One's only concern might be the low gurgles that well up from within, though this can be relaxing to the right pony. Bella's habit of being prone and her apparent friendliness allows for such an opportunity quite often, though one should be wary of spending too much time around her when she's hungry.
Bella doesn't often wear clothes, perhaps due to her size and the rather destructive effect her pudge has upon any sort of restrictive cloth. While she might occasionally be seen stuffed into a Victorian sort of getup, it rarely lasts long if there's food nearby. She has taken a liking to socks, however, and has a particular pair of black and gold-striped numbers that she can occasionally be seen in.

On top of it all, the fortunate can find a sizable pair of crotchboobs sitting just beneath her middle. Due to the many protuberances of her body, they aren't immediately obvious.