|Real name||Maxwell Tennyson|
|Nano Item||Hawaiian Shirt|
|Voiced by||Paul Eiding|
Maxwell "Max" Tennyson, better known as Grandpa Max to everyone in FusionFall, is the grandfather of both Ben Tennyson and Gwen Tennyson and took them on a cross country trip during the first series of Ben 10. He loves his grandchildren with all his heart and always makes sure to keep them happy. He is also a secret member of the intergalactic police organization called the Plumbers.
To help fight the Fusion invasion, Max is lending all of his Plumber knowledge to aid Dexter and Professor Utonium in learning more about Planet Fusion and its inhabitants. Thus Max is currently working on a satellite to survey and spy on Planet Fusion. Fuse is all too aware of this plot, and constantly sends his forces to sabotage Max's project.
Grandpa Max is stationed alongside Numbuh One and The Scotsman in the ruins of Townsville Park and can also be located in ship's interior giving the Rath Nano mission, "Let Me Tell You About Rath!" He studies the giant Fissure torn in the middle of the park which is the area's Infected Zone. He suspects that Fuse is trying to awaken an ancient beast lying deep inside the Fissure. Many of Max's missions involve traveling into the Infected Zone (The Fissure) to impede Fuse's efforts. He also gives out the "Two Bens Are Better Than One" mission that supplies players with the Albedo Nano. It is mentioned he is good friends with Plumber Nathan and Plumber Carol.