Jimmy's magic patch

Describes a fabric patch with mismatched patterns that's been sewn onto damaged fabric to fix the clothing. British WW2 slang named after a comic strip called "Jimmy and his Magic Patch" that appeared in The Beano in 1944, a story about a schoolboy who frequently time-traveled by accident thanks to a patch sewn on the back of his school trousers.

My jacket's right elbow ripped, but luckily, I sewed it up with Jimmy's magic patch.