Updated: October 28, 2018

Grandpa keeps a laboratory in the cellar of the house, and often refers to "going down to the lab." The potions and magic spells he devises there are central to many of the show's stories. Many of his inventions are less than successful, but he never stops thinking up new ones.

Grandpa can transform himself into a wolf or a bat, as per Bram Stoker's Dracula. In "Herman's Sorority Caper" and Munster, Go Home! it is revealed that he takes special pills to turn himself into these creatures. In later episodes however, and in all episodes of The Munsters Today he changes to and from a bat simply at will.

Grandpa has an extremely sarcastic personality, and often insults his son-in-law Herman. Despite this, Grandpa and Herman are quite close; in one episode, Lily says that if not for Herman, Grandpa would be "living in a cave picking fleas out of his wings". Most of the Munsters episodes revolve around the zany schemes Grandpa and Herman concoct, which either end successfully or result in Lily scolding the two for their failure. This was a comedic strength of the show that followed on from The Munsters to The Munsters Today.

While Grandpa is generally considered the wisest member of the family, he also has a decidedly stubborn streak. If he feels he isn't getting his due respect, he will let everyone know it, and often sulk or go to extreme lengths to demonstrate his offense at a perceived slight. While generally a successful mad scientist and magician, he shows a somewhat sloppy approach to his craft, often proceeding with unwise experiments, without taking sensible precautions.

Grandpa is depicted as a goofish yet loveable mad scientist. He has a pet bat named Igor who "hangs around" in Grandpa's lab. And much like a bat, Grandpa sleeps hanging upside down from the ceiling: usually in the living room, the attic, or the lab (the interior of his bedroom was never shown on the series). In The Munsters Today, Grandpa's companion was Leonard the skeleton, whom he met at college back in Transylvania. Flashbacks to the events at college and to how Leonard and Grandpa met are part of the storyline in The Munsters Today episode "Never Say Die" (airdate: February 24, 1990).

Grandpa doesn't always display the traits that are commonly associated with vampires. For example, in one episode of The Munsters he looks in the mirror and casts a reflection. However, he does not cast a reflection in later incarnations, fan fiction or The Munsters Today - neither does he appear on film, or in pictures. Traditionally, vampires do not cast reflections.

A running gag on the show, later adopted in The Munsters Today, is Grandpa's attempts to bite someone on the arm which usually ends in failure.