h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

In America a "Melvin" is the same thing as a "Wedgie". An "Atomic Wedgie" leaves the victim unable to walk for several days and involves the cloth actually beginning to saw the individual in half. Boxer Shorts are not as good for Wedgies as "Tighty Whities" (the tighter version of undewear with the elastic around the leg holes).

To "Pants" someone, like our Australian friends, is to walk up behind some poor kid in the gym and yank his pants down around his ankles, leaving him standing in his underwear (or naked, depending on his personal sense of style) ready for some really good ridicule. If you are prepared beforehand you'll have someone ready with a camera to record the moment for posterity and the school yearbook.

FYI - To "Go Commando" is to wear pants but forgo underwear. Also known as "Au Natural".

In England the practice of removing someone's trousers without their permission is known as 'de-bagging',( from yet another word for trousers ). This is popular among college undergrads.

Ah yes, the atomic wedgie, properly done (ouch!) required that the rear side of the underpants' elastic waistband actually be pulled up on top of the unfortunate victim's head.

I would just like to mention that I too found the obscure Flying Circus reference amusing (footnote @6), and to confirm that it comes from Arthur Figgis (Graeme Chapman) presenting a tribute to Johann
Gambleputty de Von Ausmere Spleden-Schlitt etc etc etc of Ulm. Also, slower, automatic wedgies, when undergarments rise up of their own accord to impinge upon scrotal substances, can be quite awkward in public (Oh! Betty swollocks?).

Re: "going Commando" etc . . . in Australia, I believe it's most commonly known as "freeballing" for, ahem, obvious reasons. But, being a girl, I'm no expert on the matter (honestly, Mum!).