Harry Potter and the Order of the Phoenix
Willy Widdershins is responsible for a wave of anti-Muggle pranking that Mr. Weasley mentions while he and Harry walk through the Ministry of Magic. Apparently, someone has been enchanting toilets to regurgitate (gross!). Unfortunately, Willy is in the Hog's Head Inn when Hermione calls the first organizational meeting of the D.A. He overhears everything they say and reports it to Professor Umbridge. Professor Umbridge tries to use Willy's evidence to prove that Hermione, Harry, and all of the other students on the D.A. list have been holding regular secret meetings against Ministry rules. But, it turns out that, in exchange for this testimony from Willy Widdershins, Professor Umbridge has dismissed all of the charges against Willy Widdershins for his toilet hexes. It's a corrupt case of I'll-scratch-your-back-if-you-scratch-mine. As Professor McGonagall exclaims, "What an interesting insight into our criminal justice system!" (27.157).