Mr. Posh Penny Abercrombie is the evil mayor and the owner of the Dog Training School who works with the villains, Cuthbert Cringeworthy, Teacher, Slasher Brown, Slasher Brown's Henchmen, The Colonel, The Inspector, Captain Prefab, Clint Katzenberger, Sergeant Slipper, Vilhemina Slop Bucket, Fatty Fudge, Reg Trademark, Captain Trout and Sergeant Boot, and hypnotises dogs with a ray gun in The Day They Took Gnasher Away and Skull and Crossbones. He is voiced by Hugh Laurie.
Posh Penny promises Dennis's Dad that he can turn Gnasher into a perfect pooch, but the Dog Training School is really a prison called Beanotown Dogs' Prison, and Dennis rushes there along with Curly and Pie-Face to rescue Gnasher from the school (as a fake dog called Trojan).
He and his friend The Security Guard are shown to be burglars and hypnotise dogs with a ray gun into helping them succeed. When their cover is foiled, the Menaces beat Posh Penny and send them to jail.