Grandma Margaret Mack is a long time Greenpoint widow; she resides at 546 Orange Drive and has owned and run Mack's Market for twenty-five years with the help of the Rascals sweeping the floors and delivering groceries. In her off-time, she reads them pulp fiction, renders advice and spars with them in her living room. Local realtor Mr. Pennypacker wants to buy her market out from under her for the property it sits on, but Grandma Mack's vision is so bad that that she signs the wrong papers to sell it to him. She instead sells it to A & B Chain Stores, Inc., but she doesn't have the money yet or has lost it when her son-in-law, Dan, comes by with his second wife. He wants to kick her out of her house and send her to the Poor Farm, but it turns out that Grandma Mack's gold bonds for the Imperial Steel Company, once thought worthless, are suddenly worth a lot of money. Realizing their worth, Dan tries to get them back from Chubby Chaney who has tied them into the tail of his kite. Without her eyeglasses, Grandma reads about the worth of the bonds in a letter from Imperial Steel through her fish tank and rushes to Chubby's rescue, devoutly giving Dan the punishment and embarrassment he deserves.
Grandma Mack's last name changes to Mann when she returns in Fly My Kite. Although several characters in the series have had various last names, Butch and Miss Jones for example in the haphazard continuity, here it can presumed Mann is her maiden name and Mack was the name she shared with her husband. This would imply the character acquired the bonds when she was single or her late husband bought them under her maiden name as a inheritance.
Grandma Mack was played by Margaret Mack.