A gunman wearing a onesie of Adventure Time character Jake the Dog has robbed a Bundaberg service station early this morning.

The offender entered the United service station on the corner of Boundary Street and Fe Walker Street at Kepnock just after 2:30am and threatened an employee with a gun.

Police said it was the third time the service station in Kepnock had been robbed this year. ( Supplied: Queensland Police Service )

Police said the person stole cash from the register and ran from the shop towards Farthing Street.

It was the third time the service station had been help up this year.

The offender was described as being up to 170cm tall, and was wearing the yellow onesie with black gloves, a black mask and an Adidas bum bag.

The yellow, shapeshifting dog Jake is one of the main characters of the popular Adventure Time animated series.

While one of the show's heroes, Jake has a nefarious past as a bandit and robber.

Police have urged anyone with information to come forward.