During a storm, Buster's gonads were zapped by cosmic rays which enlarged them to an enormous size, so that he needs a wheelbarrow to carry them around.
For example, in one episode Buster climbs a tree whereupon some children standing below mistake his hairy scrotum for giant horse chestnuts, deciding to pelt it with sticks and stones in order to knock it down so they can play conkers.
Finally, an endangered species of bird decides to build a nest on Buster's scrotum and lays eggs in it.
In December 1987, Viz released a 7-inch single entitled "Bags of Fun With Buster" (B-side "Scrotal Scratch Mix") by Johnny Japes and His Jesticles (in reality Andy Partridge and Dave Gregory of XTC, journalist, record producer and sometime vocalist Neville Farmer, with John Otway on vocals released on Fulchester Records).
During the Gulf War of 1991, a SEPECAT Jaguar GR1A (number XZ118 Y) bomber of the Royal Air Force featured Buster Gonad nose art.