flid flippers
Flid flippers is the practice of hiding your elbows inside your shirt, rolling up your sleeves and poking your hands out of the them. The phrase "flid flippers" is funnier than the practice.)
written by Ma*tin *and, approved by Log

Another equally hilarious way of mocking the afflicted was to double your arm up inside your sleeve so as to grip your should with your hand then rolling back the sleeve so that the ball of your elbow poked out the end like a stump. You should not make the mistake of forgetting to push your tongue into your bottom lip and making mong sounds to complete the effect. Doing this with both arms at once would really win you some serious kudos/detention.
written by Ro* You*g, approved by Log

A similar thing could be achieved by putting your arms down the wrong sleeves of your jumper and flailing wildly. Apart from ruining your jumper, this would also give you the added effect of looking grotesquely deformed.
All that was missing was a sack over your head and a friend parading you around the playground with a big stick.
written by Gr*ham*Bever*ey, approved by Ponky

To embelish the flid flippers joke, make sure that everyone stands in front of you. Perform the maneouvere, this time with the added impact of taking your shoes off and kneeling in them. This produces an excellent "fliddy dwarf" effect.
It is so funny, it is actually worth the stultifying wait for you take your shoes off, put your arms double in your shirt and tell everyone to stand in front of you. It is. I swear it is.
written by an*nymou* u*er, approved by Mansh