Over the course of 30 idents, the character, named Mini Ha Ha in reference to the character of the same name from the novel Hiawatha, travels the country telling jokes to the public.
Although the jokes feature unexpected twists, they are generally of poor quality and delivered in such an unusual dead-pan style that they are met with blank expressions from the unimpressed public.
The idents were written by Dave Cornwell, art directed by Jane Briers and directed by Leslie Ali, the joint creative director of WCRS, through Hungry Man.
Simon Peck, the group account director at WCRS, said: "With tongue firmly in cheek, we have created more than 30 individual idents, all using the Mini Ha Ha character. They fit brilliantly with the Green Wing programme."
The idents will launch on 3 September, with the first episode of Green Wing. Mini has previously sponsored the ITV shows Cold Feet and Between the Sheets.
Earlier this summer, WCRS produced a TV and poster campaign in which the Mini played the lead role in parodies of famous films such as Mutiny on the Bounty.