Max Tennyson

Max Tennyson is a semi-retired plumber who is the grandfather of Ben and Gwen. He has wielded the Omnitrix in the alternate-reality episode Gwen 10 of the original series. He is a good friend of Kevin's father. He has two sons, and their mother is Verdona Tennyson.

Backstory
Not many details are given on Max Tennyson's childhood and background:

In Permanent Retirement, Max's older sister, Vera Tennyson is introduced; she is seen as having her own weird taste in food, and is hinted as having knowledge that aliens are real. In Big Fat Alien Wedding, Max's older brother, Gordon Tennyson is introduced; in the events of the episode Gordon is also a Plumber, still on active duty, as is his wife, Betty Jean Tennyson, and their son, Joel Tennyson. A ten-year old version of Max was seen in the episode Don't Drink the Water.

In Under Wraps, Max mentions having spent his childhood summers on his Uncle Jedediah's farm, where he learned about the merits of hard work. In Last Laugh, a 'not-quite-all-there' Max, under the effects of Zombozo's happiness-draining, mentions having been afraid of heights as a kid and then, when "enough was enough", Max "climbed up to the top of the water tower" and 'scared the fear' right out of him.

In They Lurk Below, it was shown that Max had a childhood friend was called Donovan Grandsmith, who sums Max up as; "growing up he always was the worrywort...never the risk-taker", like himself. 30-years earlier, Donovan and Max had both been broke when Donovan offered Max a business opportunity which he turned down. Max later became a Plumber (Donovan thought Max was a plumber that works with plumbi8ng), establishing that Max's career as a Plumber lasted for about 28 years before he retired (Max mentioned that after 28-years on the job, he'd never figured out who was behind the Bermuda Triangle).

In the episode The Return, it was revealed that Max had been an astronaut and would have been the first man on the moon, but left the program before the Apollo Moon mission. In his own words, Max said he just 'took his step for mankind in other ways'. It is later revealed that he did in fact go into space, just not with NASA.

It is unknown if Max's strange taste in food was acquired from his adventures to other planets during his career as a Plumber, or if its root can be found in his childhood.

It was revealed in Moonstruck that Max met Verdona when she was held captive by a Synthroid (a species of robotic aliens) that wants to use her Anodite powers as fuel for their planet. Max saved Vendona who went on as his wife.

Ben 10
Grandpa Max is a Plumber, who takes his grandchildren Ben and Gwen on a cross-country trip, during which Ben discovers an alien watch, the Omnitrix. His grandson uses the watch to become the superhero "Ben 10". Max helps his grandchild fight bad guys and aliens, he also teaches Ben to use the watch responsibly. During their adventures, Gwen and Ben question Max's uncanny knowledge and the fact he doesn't seem to be bothered by all the weirdness they encounter. It is eventually revealed that Max and the alien warlord Vilgax are old enemies.

In the episode , Max reveals he is part of inter-galactic police force known as The Plumbers and that he had fought and defeat Vilgax years before. During the episode he meets his old partner Phil. He discovers Phil stole the Null Void Projector, using it to make easy money, by freeing the aliens who the Plumbers had already captured, then fighting and catching them for profit.

In the episode Perfect Day, Max has received a wedgie from Cash and JT.

In the episode The Visitor, it is revealed the Omnitrix was originally sent to Max by the alien Xylene (who was Max's old flame) and accidentally ended up in the possession of his grandson, Ben.

Ben 10: Reloaded
Max is still with his Grandkids and they are ready for Training. Before Max left his own mission for the next 2 years on Alien force. In Episode Space Red Ranger, Max Sends Andros to save Ben and his friend.

Bob 10
One of Eugene's friend. He appears An old friend he was... in Bob 10. He helps with Eugene,Bob & Gang to stop Phil.

Ben 10: Protector of the Omniverse
He appeared in The Trouble With Doubles and Escape From the Infinimatrix.He appears again in Say Hello to The Avengers.He is the founder of The Avengers(POTO).In Alpha Returns, Ben as Upchuck voice called him through the Infinimatrix.He appears as a hologram in Wrath of Vilgax.His future self appears in Ben 10,000: Return of Hex.His 60 year old self appears in To The Past.

Jimmy 10
In Jimmy 10, Max gets kidnapped by Vilgax, so Vilgax can lure Jimmy into giving him the Decatrix.

ben 10 omni alien
max tennyson is a main character in ben 10 omni alien and he is more powerful than he was in ultimate alien and he has been ranked up to station commander of the plumbers head quarters.

Ben 10: Unlimited Power
Max Tennyson was a minor character in Ben 10: Unlimited Power, only appearing in one episode. He appeared in The Siege of the Earth Part 1, the 1st part of the Season 1 finale. He was killed in the very same episode.

Chris 10: Aliens Unleashed
Max is chris's grandfather and a minor character. He helps out on missions and guides the team through trouble. He took them out camping one night where chris found the ultimatrix.

Noah 10
In Noah 10, he never retired and is still at his rank of Magister. He trained Noah when he became a Plumber. He is Noah's commanding officer and mentor. He often gives Noah missions.

Ben 10: Alien Universe
Max Tennyson appears in the second season episode "Clancy Strikes Back!" in Ben 10: Alien Universe.