This version of arrrrrrrr is followed up with an identically-drawled "bar-barrrrrr". We did this because we thought a "bar-barrrrrr" was a poo. Curiously, so did all the teachers, who wasted no time in royally bollocking us if they heard someone saying it. This of course led to a cyclic form where someone would do something bad, someone else would say "arrrrrrrr bar-barrrrrr" to them, then everyone else would turn to that person and say "arrrrrrrr bar-barrrrrr", and then to each other, and so on and so forth. Mass hysteria, particularly in the heavily-regimented and dinner-lady-policed lunch queues, would often result.