Åhlin started his career as an artist for the Hasse & Tage production Svenska bilder from 1964.

In 1970 he started his own animation studio, PennFilm Studio AB situated in Hököpinge, and directed many feature-length films and several shorts, including Sagan om Karl-Bertil Jonssons julafton which is shown on television every Christmas Eve in Sweden, Norway, and Finland.

He has commented on the difficulties of making animated films with adult themes: "I don't know whether the problem lies in the audience or the marketing.

As of 2009, Åhlin had said that he still occasionally worked on the project on his own: "Hopefully it can become a few minutes which can give potential producers remorse in the future".

[6][7] Other unfinished films include Den magiska saxofonen ("The magic saxophone"), HC Andersen, and an adaptation of Eric Linklater's The Wind on the Moon, with a screenplay by Ulf Stark.