Theobromine poisoning is also known as chocolate poisoning and it is common in animals such as cats and dogs. It is not common in humans since humans do not tend to ingest large amounts chocolate.

Bianca fed Wellard some chocolate causing him to suffer theobromine poisoning and he had to be put to sleep.

Chocolate contains cocoa, and cocoa contains the compound theobromine. Theobromine is toxic to dogs and other animals at certain doses. Chocolate poisoning is a problem that occurs mainly in dogs but also occurs occasionally in cats or other animals.

Chocolate contains a chemical called Theobromine. Large amounts of this can cause Theobromine poisoning, the symptoms of which start with sweating, trembling and headaches, and can end with heart failure.

Humans metabolise Theobromine quickly - fast enough that only long term accumulation, or a large amount eaten quickly, will have an effect on us. Other animals, including dogs, metabolise it much more slowly. Domestic pets are most the most likely non-human animals to have the opportunity to consume chocolate, and dogs are the most likely out of those due to their tendencies to scavenge anything that's within reach. So it can indeed cause a fatal poisoning, when a dog consumes a human-sized portion of chocolate.

Dogs have a slow digestive system and chocolate is very thick so it take time for a dog to digest it and eating too much can cause severe stomach problems.