The City Centre Piazza will be showing the 1939 classic The Wizard of Oz on Sunday (June 27th) and council officials hope as many people as possible will turn up in children's fancy dress or adult costumes.
As an added incentive, there will be a prize for the best dressed, with judging set to take place before the film starts at 13:00 BST.
So if you're going to be in the Plymouth area, why not put on your Scarecrow fancy dress costume and see if you can wow them all?
Councillor Vivien Pengelly, leader of Plymouth City Council, said: "We've got high hopes for the fancy dress competition and we're hoping to see lots of cowardly lions, silly scarecrows and many many Dorothys."
The country seems to have gone Wizard of Oz mad ahead of the opening of the new West End musical in March next year!