Uncle Fester is a completely hairless, hunched, and barrel-shaped man with dark, sunken eyes and often a deranged smile. He always wears a heavy, full-length fur coat. Fester was derived from a character drawn by cartoonist Charles Addams, although these were single-page cartoons, with no stories or character names. Nevertheless, the character is recognizable in a number of cartoons, both by his appearance (bald, stooping, sunken eyes) and behavior (e.g. turning the shower to a special “scalding” setting, feeding his garden plants blood plasma, and releasing an eagle on the neighbor’s homing pigeons). While he is occasionally seen with the rest of the family, particularly on anthology covers, he is also seen on his own more often than the others. He is sometimes indicated to live in a small shack surrounded by a wrought-iron fence.

Fester has a strange ability to generate electricity. He would often demonstrate this by putting a light bulb in his mouth, which would illuminate, accompanied by a loud, crackling noise. He claims to possess 110 volts of power in one episode of the sitcom, while in another episode he demonstrated his “magnetic” quality by levitating a metal paperweight up to his hand. When struck directly on the head by a fired cannonball, he appears only mildly dazed, while the cannonball bounces off his head.

Uncle Fester at times has severe migraines but appears to enjoy them. Fester relieves his migraines by placing his head in a large screw press and tightening it to levels that normal people would not be able to withstand. At times, Fester uses the screw press on his head simply for enjoyment.

Despite Uncle Fester’s menacing look and bizarre behavior, he is gentle and caring to everyone. He shows great respect to Gomez and Morticia. He has always exhibited love and great care to his niece and nephews, despite their frequent naughtiness.

In the original sitcom of the 1960s, Fester is said to be Morticia’s maternal uncle (his name rhymes with Morticia’s mother Hester’s), but from the 1970s onward, he is Gomez’s brother. In all adaptations, he is either uncle or great-uncle to Wednesday and Pugsley.