According to "The Official Handbook of the Marvel Universe: Update '89", it is conceivable that the Slug is actually a mutant, inasmuch as it is difficult to imagine how a normal person could achieve such tremendous mass and still remain alive. Unlike Blob, the Slug has no means of compensating for this mass, so he is almost immobile when not making use of a high-tech personal hovercraft. The Slug's high percentage of fat enables him to float effortlessly in water. His metabolism grants him limited immunity to drugs and poisons. The Slug has been known on occasion to asphyxiate his victims (usually underlings who failed or displeased him) in the folds of his flesh. The Slug is extraordinarily obese, so much so that he is unable to support his own weight by standing and is unable to move his body mass under his own power. He needs to consume vast quantities of food and liquid every day, so he eats during most of his waking moments. The Slug has extremely light-sensitive eyes, causing him to wear shaded eyeglasses virtually all the time. Slug rides special custom-designed heavy-duty electric wheelchair/forklifts fitted with tank treads or heavy tires. His chairs appear to operate by remote control, and often feature built-in flotation devices or rocket boosters for air escape. For longer distances, the Slug rides in a custom semi-trailer.