Is it a wrinkly bird? Is it a plane with a blue rinse? No! It's SuperNan! 

When Young Josh is sent to stay with his geriatric grandmother he expects a weekend of endless tedium only interrupted by tedious knitting. If only his grandmother was more like his hero, that caped crime fighter, SuperNan.

What Josh doesn't know is that SuperNan and his own seemingly frail Grandmother are one and the same.