The pig trick
Not described, but it evoked cries of "not in front of the children!" and "without a pig?". It was still good enough to win Petulia Gristle the Witch Trials. Although admittedly only two witches officially took part and Granny Weatherwax was sitting in the front stalls... although Granny was seen to nod approval, no small thing in the world of competitive witchcraft.