What a Whopper(1961)

Naughty Maids And Naughtical Monsters, A Book! A Monster! A Film!

A writer attempts to raise some cash by writing a book about the Loch Ness Monster. No publisher will take it because they all think there isn't really a monster. The writer and some of his friends make a fake monster and take photographs and then travel to Scotland to see if they can convince the locals.