The Beer Can Aleins are an alien species that look like giant beer cans, albeit with arms and legs. They began to consider earthlings as enemies after Rat said that his personal goal was "To drink your head."
The Beer Can Aliens later appeared in a storyline where Pig and Guard Duck were lost in space. They threw oxygen tanks at them, in retailiation for Rat's offenses. This had the result of saving Pig and Guard Duck, although they were attempting to hurt them.