Domestic ducks nearly all originate from mallard ducks that were first domesticated at least 4 centuries ago. They can -and are- kept as pets in a garden or a backyard, but it should be noted that they should have access to either a pond, or a deep water dish. Ducks can be kept as free range pets and fed on a grain and insect diet to stay healthy.
Domestic ducks are notoriously unreliable at incubating their own eggs and will often just walk away. Because of this, it has become normal on farms to put the eggs under a chicken so that they can incubate. Selective breeding has also produced breeds with crests or strikingly coloured feathers. These ducks can often be entered into show competitions and exhibitions.
There have been a number of children's books written that have used a duck as one of the main characters. Even TV has seen its share of famous ducks, such as some of our favourite cartoon characters, Daffy Duck and Donald duck.