Joseph Longtarin is a policeman working in the neighborhood where the Spirou office is located. He is one of Gaston's favorite "victims". Gaston and his friends destroy his precious parking meters, by replacing them with candy dispensers, or by installing a remote control system in order that they no longer have "to feed the dreaded money-eating machine".

In return, Longtarin gets on Gaston’s case: he examines his new vehicles with a fine-toothed comb to make sure they meet up with the standards of the law; he especially keeps watch on the parking meters at which Gaston is parked and puts his energy into writing Gaston tickets for as many infractions as possible.

However, Longtarin is not heartless: when Gaston and his friends set out to grow a tree around one of the meters, a tree where birds had made their nest, Longtarin decided (under the pressure of Gaston and his friends) that anybody wishing to park in that space must pay their toll in food for the baby birds.

Aimé De Mesmaeker, or Monsieur De Mesmaeker, is a rich business man. He is always seen trying to sign an important contract with Fantasio or Prunelle. But without fail, Gaston always manages to mess up the signing of the contracts. However, De Mesmaeker sometimes appreciates what Gaston does, like when he proposed a contract for the sale of Gaston's vegetable soup.

De Mesmaeker was the last name of Johan De Mesmaeker (known as Jidéhem from the French pronunciation of his initials J.D.M.), one of Franquin’s frequent collaborators, who remarked that the character looked like his own father.