Slimy Sammy is Perfect Peter's so called 'pen pal from France' who tries to use Horrid Henry and get him in trouble. He tries to steal Peter's stamp album but Mum catches him red-handed, subsequently sending him home to France with his parents. He has brown hair, wears a pale red jacket with a dark magenta tie, white shirt, and gray trousers. He is voiced by Aidan Cook.
In Perfect Peter's Pen Pal, he was best friends with Peter until he turned on him and tried to escape with his stamps. He also had other pen pals in the past and were friends with them, though he revealed he turned against them as well. He was three years older than Peter.
In Series 4, He returns and from Horrid Henry Eco Warrior, he helps Peter.