Even when I was in school we still used the customary Joey Deacon spastic impression.
And it was for this that the headmaster of my primary school pulled me, and a group of mates into his office for 'bullying'.
By way of 'punishment' he proceeded to perform the most outrageous impression of a handicapped since Daniel Day Lewis:
He flailed his arms and legs all over the place, whilst spitting and drooling, and made primitive grunting and hooting noises.
His idea was to shock us into realising how unpleasant we had been, but the result was simply 4 naughty boys with tears rolling down their faces as they dismally failed to stifle their astonished, choking laughter.