Did you ever hear of the classic children's movie, "The Wizard of Oz"? Made in USA, I believe, it was one of the first musical/"talky" big-production movies that was MOSTLY in color rather than black & white. If you haven't heard of it, the Reader's Digest version is teenage girl, Dorothy (Judy Garland), & her dog Toto are transported via tornado to a distant magical land that is ruled by a reportedly all-powerful Wizard that resides in the city of Oz. She is advised to go see the Wizard to see if he can help her get back home. On the way to the city of Oz, she is joined by a scarecrow that wants a brain*, a tinman that wants a heart, and a cowardly lion that wants courage. The movie follows the little groups' adventures & encounters with such things as magical forests, wicked witches, and other fantasies in their trek to see the Wizard to get their requests fulfilled. Practically every kid in the USA has probably seen it at least a few times -- I did when I was a kid! I'm a little surprised this flick hasn't made it to the UK! ...Or maybe you just needed your memory jogged!
I just don't think I'd have made the connection even if I had remembered it. When was it - 1939?
It's funny you know, but its the great divide again! Popular culture, particularly TV, is still quite different. You may buy our films & TV programmes and we do the same from you. However the catch phrases and expressions that we retain are totally different.
For example, from Minder the term - 'er indoors (meaning the wife) is almost part of the language.
"I don't believe it" "Here's one I made earlier" "Gissas a job" "Bob will fix it!"
are all probably uniquely British
However "Phone a friend?" "You are the weakest link - goodbye" probably made it intact over to you.
I just don't think I'd have made the connection even if I had remembered it. When was it - 1939?
Don't remember the date. I must admit, I didn't get it when I first read it. First you must make the leap from "scarecrow" & "wizard" to the Wizard of Oz story/movie. Then there's the implication the shirt wearer makes that the shirt reader has joined the group traveling to Oz to, like the scarecrow, request a brain. Thusly, the punchline on the shirt becomes understandable. Maybe I'm attracted to punchlines that aren't immediately apparent or understood by everyone! Anyway, when the light dawned in my own mind, I literally LOL and thought I'd share it with yous guys!
Anyway, when the light dawned in my own mind, I literally LOL and thought I'd share it with yous guys! 
Same seller also has an "ebay sniper" t-shirt 