Stanley Howler is the strange young man in Going Postal, who Moist von Lipwig encounters at the Post Office. He was orphaned when his parents passed away of the Gnats (a kind of plague) and was raised by peas. Not on peas, but actually by peas - which has left him as a bit of a loner, an obsessive, and with a tendency to lean towards the sunlight.
When Moist arrives at the Post Office, Stanley and Tolliver Groat are the only employees left. They are roommates who are polar opposites, one with a messy side to his room and the other super neat which resonates with films such as The Odd Couple (TV and movie) and the Buffy the Vampire Slayer episode Living Conditions (Pratchett was probably not consciously thinking of the latter, not being a fan). When Moist von Lipwig, the new Postmaster, first meets him he is the more obsessive of Ankh-Morpork's large number of pin collectors (called 'pinheads'), to the point that all the other collectors think he is "a bit weird about pins". Stanley exhibits some of the tendencies of autism in his encyclopedic knowledge of pins and obsessive nature toward them. He wears a T-shirt emblazoned "Ask me about Pins" and is the editor of the magazine "Total Pins" and hates the rival magazine "Pins Monthly", both popular names for magazines (except for the pins part). He has "little moments", when upset and all hell breaks loose unless Tolliver is nearby to redirect him who looks after him.
But when stamps enter his life, Stanley puts away his childish fascination with pins and the whole glorious world of stamps opens before him, a new obsession. Moist makes him the Head of the Stamps department at the Post Office at which he excels. He becomes Ankh-Morpork's first stamp collector and quickly grasps the realities of stamp collecting. He makes sure that the new stamps for Sto Helit have lots of mistakes in the first printing to increase their value and develops the idea of 'first day covers'. He saves Tolliver's life when the banshee, Mr Gryle mistakes Tolliver for the Postmaster Moist von Lipwig because he happens to be wearing the Postmaster's hat at the time. He has "a little moment' and whacks the banshee with a bag of pins, then drags Tolliver to the staff room away from the fire, which Mr. Gryle has set in the Post Office.
- Stanley, who was raised by peas draws a ridiculous parallel to the many "true stories" of children being raised by animals as well as fictional accounts such as Rudyard Kipling's Jungle Book boy, Mowgli, who was raised by the wolf pack, or Edgar Rice Burrough's Tarzan of the Apes, or Romulus and Remus the founders of Rome raised by wolves.
- Stanley's surname was not revealed in Going Postal, but was initially given in official materials relating to Discworld stamps, and later confirmed in Making Money. The name is a reference to Roundworld's Stanley Gibbons (Howler Monkeys and Gibbons are both types of monkey) - a London firm who specialise in stamps and stamp-collecting.
In the TV adaptation of Going Postal, Stanley is played by Ian Bonar.