The Senior Citizen Squad are a group of senior citizens led by Numbuh 2's grandmother, Lydia Gilligan who use 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 Kids Next Door. Later, when they attack the Sector V Treehouse, the effects of the anti-aging cream wear off and their true identities are revealed.
Maurice, Sheldon and Lydia use their wheelchair (referred to as "Gentitron"), walker (referred to as "Sahpilator") and walking stick (referred to as "Grandmachine"), respectively, as equipment in battle. In their older forms, they can combine these three devices to create a small mech called "Senior Citizen".
While the Senior Citizen Squad don't particularly like the KND, they are mostly concerned with their personal affairs like eating tapioca and use their abilities in villainous ways towards that end rather than to destroy the Kids Next Door. However, their teenage forms were seen at Mr. Boss' Annual "We Hate the Kids Next Door" barbecue in Operation: A.F.L.O.A.T..
In Operation: L.U.N.C.H., Lydia, Sheldon and Maurice spring into action as the Senior Citizen Squad to beat up Robin Food after he gives them unwanted junk food stolen from kids' lunches. They last appeared in Operation: I.N.T.E.R.V.I.E.W.S., where they came to the amusement park to get the Delightful Children's cake, but decided to leave when they heard they had to do a scavenger hunt, while all the villains decided to play.
- Based on the name of their group, it could be implied that they are high school seniors when they transform into their teenage forms, hence the word "Senior" in the name of their group.