Grandma Lydia is the mother of Betty Gilligan and the maternal grandmother of Numbuh 2 and his brother, Tommy. She lives with her daughter and grandsons, and is also the leader of the Senior Citizen Squad. Lydia appears to have an anger problem and often hits people with her walking cane.
Lydia used an anti-aging cream that turns them into very physically agile teenagers. Apart from Lydia, the group consists of Sheldon and Maurice. The Senior Citizen Squad first appears in Operation: T.A.P.I.O.C.A., where they are first seen hijacking a truck of Tapioca Pudding and being attacked and defeated by the Sector V operatives. Later, when they attack the Sector V Treehouse, the effects of the anti-aging cream wear off and their true identities are revealed.