Roobarb is a green dog, and Custard is a pink cat. Roobarb is always involved in some kind of misadventure which he approaches with unbounded enthusiasm. Custard is cynical and sets out to sabotage Roobarb's fun. Other characters in the series are the birds, who watch the antics of the other two from the safety of a nearby tree, often making snide remarks, and siding with whoever is winning.
Fun Fact - Roobarb was the first fully animated television series to be made in the United Kingdom!