Mr. and Mrs. Twit are the titular villains of the Roald Dahl children's book "The Twits" - they are a married couple but share little in the way of love and are constantly depicted as extremely nasty and antagonistic towards each other and everyone around themselves.
Mr. and Mrs. Twit are revolting, both on a physical and moral level, they take no pride in their appearance and as a result are filthy and grotesque - they also love to play horrible, cruel pranks on one another that are more suited to schoolyard bullies than a married couple.
The couple also enjoy being cruel to animals, using glue to capture birds that nest on their tree to make into bird pie and forcing their pet monkeys to stand upside down on top of one another for prolonged periods of time - Mrs. Twit also takes to carrying around a walking stick for the specific purpose of hitting any small animals or children that get in her way.
However when the mysterious Roly-Poly Bird arrived from Africa it helped the monkeys and birds to get revenge on Mr. and Mrs. Twit, the animals waited until the pair had left the house and quickly used glue to stick all the furniture to the ceiling.
When Mr. and Mrs. Twit came back a pair of ravens quickly flew past and stuck glue on the two villains heads but they were too stupid to realise, in fact Mr. and Mrs. Twit were so incredibly stupid that upon seeing their furniture on the ceiling they panicked - believing they were somehow upside down themselves.
To remedy this the two quickly stand on their heads but due to the glue end up stuck that way as the animals rejoice - the Roly-Poly Bird helps the monkeys to return to Africa while Mr. and Mrs. Twit ultimately meet a grisly end as their bodies collapse in on themselves over time until nothing is left of the gruesome pair save their clothes.