Wonder-Gran is a costumed crime-fighter in England. Not much is known about her past, but she has greater strength and speed than any other grandma her age. She could lift barbells and throw around full-grown men. She was impervious to harm except in her toes which when Dr. Jackal stomped on them, requiring her to lean on an assault rifle disguised as a crutch. She could blow up airplanes with a slingshot and speed around on a jet-powered bicycle. She was able to walk sideways up walls.
Wonder-Gran was the ally of the local police force who often called upon her when crimes were occurring. She first appeared when Dracula arrived in London fleeing from his wife, and the police called upon Wonder-Gran to battle the aging vampire. Wonder Gran managed to use a photograph of Nicholas Parsons to ward him off, but he found himself just one more victim before villagers arrived to chase him off.
When Dr. Jackal launched a crime spree as Mister Hyde by picking pockets and committing public scams to steal all he could, the police once again called upon Wonder Gran to stop the villain. She blasted Mister Hyde and his gang with a cannon when they came to rob the bank where she was working and pursued them to St. Eamon's Golf Club where Hyde and his gang harassed and robbed the members. The police came to stop the fracas, and Wonder-Gran took Mister Hyde home to reform him, but he was a bull in a china shop as he distractingly wrecked and smashed up her modest home. Once he got food into his stomach to counteract Jackal's potion, he reverted back to kindly and misunderstood Dr. Jackal. The presence of the normal looking doctor frightened Wonder Gran so badly she rode away on her jet-powered bicycle.
- Wonder-Gran was played by actress Sue Upton.
- This character is possibly a spoof of the 1975 to 1979 American TV series "Wonder Woman" with actress Lunda Carter.
- Sue Upton also played little old ladies in Big Poppa, Fingers McNee and Holiday.
- In "The Benny Hill Story" biography, it is revealed that the objects Sue is attacked with in "Wonder-Gran vs Mr Hyde" were made from balsa wood and polystyrene; yet, they still must have hurt because she broke into tears when Dennis yelled "Cut!"
- Through the sketch, several locations from other sketches are seen. The bench scene is on the field from the Keep Fit Brigade, the fence along the road is Jed Jardine's country road in Big Poppa and part of the chase scene occurs near the mansion at the star of the Scouts and Guides Annual Fete. Wonder-Gran's cottage stays in the background of nearly all the park scenes.