Maxwell "Max" Tennyson aka Grandpa Max as his grandchildren call him, is the paternal grandfather of Ben, Gwen, Kenny and father of Carl Tennyson and Frank Tennyson. He is in his late 50's to early 60's to mid 60's (64-65 in Alien Force and 65-66 in Ultimate Alien), rather overweight and a bit slow at times, but with a keen sense for adventure and a strange taste in food. Max ends up taking the kids on a Summer Vacation Roadtrip across the United States. Much to Ben's annoyance, Ben discovers that Gwen is joining them. Max travels in a motor home nicknamed the Rust Bucket, which he has modified with advanced technology. The Rust Bucket is a replica of a GMC Classic Motor home.
Max is a semi-retired legendary Plumber, is the mentor of Ben, Gwen and Kevin and the Plumber Helpers. According to Azmuth, Max is widely considered the greatest plumber in the Milky Way Galaxy. Max is currently Magister of Earth.
Although Max doesn't have any super powers, he is very skilled in combat and can take on anyone who does have them as he is quite athletic for someone of his age. As a retired plumber, he has access to a variaty of various plumber tools and weaponry which he uses skillfully. Aside from that, his experience from his plumber days made him knowledgeable on various species of aliens. He is also able strategise well and is skilled in inventing machines. In Moonstruck, it is shown that he is telepathically connected to his wife, Verdona.
Maxwell "Max" Tennyson in the original series wears a white shirt, coverd by a red button up shirt with a floral design. He has grey hair and blue pants as well as black shoes.
In Alien Force Max's appearance did not change except for his blue pants have changed to brown, he has more wrinkles, a slightly darker shirt, and whiter hair.
Again in Ben 10: Omniverse his appearance has not changed that much except for his brown pants have changed to white. He has whiter hair and more wrinkles. His white shirt that he wore under his red button up shirt has changed to black. Also, his shoes are now grey at the top and black at the bottom.
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 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 plumbing), 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 Verdona and Magister Labrid, the latter of whom recruited him as a Plumber.
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 Truth, 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.
Ben 10: Alien Force
In Ben 10: Alien Force, Max looks mostly the same, save for more wrinkles and a darker red shirt with whiter hair. In the episode Ben 10 Returns, he leaves a transmission for Ben stating that he is investigating renewed alien activity on Earth and claims that he has the Omnitrix. An image of a DNAlien flickers at the end of the transmission. It is conceivable from this, that Max was wearing an ID-Mask and that the DNAlien in the teaser was actually Max (the voice of the DNAlien is confirmed as Paul Eiding), implicating himself as a mole to distract the Highbreed from Ben (whom, with the Omnitrix, poses a greater threat). The message was probably in code, telling Ben to put on the Omnitrix once more. An earlier theory suggested that the hologram might have been that of a DNAlien who wanted to keep Ben out of their business, but instead made a big mistake.In the episode Max Out, Max destroys a Xenocyte hatchery by detonating a Null Void Projector, which after removing its focusing lens, makes a "pretty good imitation of a hand grenade" and produces an explosion that covers over half a mile wide. Max appeared to have been killed in the blast, but was instead sent to the Null Void (episode: Voided), where he, calling himself "The Wrench", fought Dr. Animo, who was calling himself "D'Void". He has since appeared in the two-part episode War of the Worlds to aid Ben in his battle with the Highbreed along with the "Plumber Helpers". At the end he takes on the Plumber kids who fought with Ben as his apprentices. He and the Plumber Kids also appear in the two-part episode Vengeance of Vilgax.
In the episode If All Else Fails, it is revealed that the Highbreed had infected him with a dormant seed which was part of a failsafe plan of the Highbreed. It is mistakenly activated by a Highbreed Officer, who was unaware that the Highbreed has called-off the war. Max is freed from the seeds' control by Ben, Gwen and Kevin. Also during the episode, he mentions he knew Kevin's father, Devin Levin.
In Above and Beyond, it is revealed by Pierce that Max is now the earth's Magister (an equivalent to 'Colonel', likely assigned as earth's Magister after the Highbreed conflict, during which the former Magister Labrid was killed). In the episode, Max set up a scenario in which Ben was to go on a rampage on board an orbiting Plumbers' space station. He then calls the Plumbers' Helpers to come and save him. They manage to defeat Ben, but the battle had caused the space station to fall out of orbit towards the city of London. The Plumbers' Helpers decide to activate the station's self-destruct, which would mean sacrificing their lives in the process. However, the space station doesn't explode. Instead, Max appears along with Ben, who reveals to the Plumbers' Helpers that the space station is a Plumber Training Facility and that Ben's "rampage" was set up to test them. Max also states that by putting "the safety of others ahead of their own lives", the Helpers will be admitted to Plumbers' Academy.
In the season finale, The Final Battle, Max takes part in the fight against Vilgax. When Kevin returns to his human form, Max states that the Omnitrix kept him in his mutated form. Max aids Gwen in trying to stop the ship from crashing into Bellwood. After Ben escapes from Vilgax, he, Gwen, and Kevin share a group hug with Max.
Ben 10: Ultimate Alien
Max has grown to his full potential and is now wiser than in any other series. Since Alien Force, he's been trying to be protective around Ben, Gwen and Kevin. He makes his first reappearance in the episode Hit 'Em Where They Live, it is revealed that Max has been protecting Ben's parents from being attacked by Ben's old enemies (due to Ben's secret being revealed to the universe). However he is injured while protecting Sandra from Sevenseven and is forced to inform Ben and his team of the problem.
Max appeared again in Ultimate Aggregor and Map of Infinity, where he helps Ben, Gwen and Kevin stop Aggregor. However, in the beginning of Map of Infinity, Ultimate Aggregor's electrical shock damaged his entire nervous system, and must be replaced. Azmuth brings him along side with Ben and his team to Galvan Mark II, where Max is placed in a tube that would repair his nervous system after a few weeks. Max returns in Absolute Power with his Magister's Suit, his nervous system having been fully restored and helps Ben and Gwen in the battle to stop Ultimate Kevin.
Grandpa Max returns in Moonstruck, where he reveals his past where he met Verdona to Ben, Gwen and Kevin (who sleeps after hearing the story). When he was about Kevin's age (16 or 17), he was a pilot in the air force. During a mission, he saw and followed a space ship. He blasted it but the space ship got away and Max's plane crashed. He talked to the Commander about the space ship, which made him an astronaut and gave him a mission to be the first man on the moon. While at a saloon, he met Verdona in her human form and fell in love with her. Suddenly a giant human robot came and attacked Verdona. Max saved her and left to a far away desert where the robot couldn't find them. Verdona explained to Max that she is not from earth, she is from another planet. The robot that chased them was a sentient robot called a Synthroid and it left a bracelet on Verdona's hand which made her unable to do most her powers except her telepathic powers. She revealed to Max that she was the one in the spaceship he saw before she read Max's mind. She told him that their minds are now linked. She also revealed that the Synthroid wants her to be a battery-like energy source for their planet (since she is an energy being). The Synthroid came back and kidnapped Verdona but Max used his mind to located Verdona (since Verdona said their minds are now linked). He (with a help from Magister Labrid) saved Verdona and destroyed the Synthroid. Verdona invited Max to her planet but Max denied the offer, saying that he has other things on earth. They kissed and Verdona left. The next Monday he went into the astronaut training eventually Max joined the Plumbers after Magister Labrid recruited him. He told Ben that was the story of how he and Verdona met later noting Max and Verdona getting married is another story and said good night to Verdona before he went to sleep.
Max appeared once more Prisoner #775 is Missing when Area 51 was attacked and was furious when he learn of its alien prisoners being held there illegally and as a result had caused friction between Rozum and Max
Ben 10: Omniverse
- 4 inch Alien Collection Max Tennyson (Alien Force)
By the age of 80, Max has further modified his RV, grown a beard, and replaced one of his arms with a cybernetic prosthetic. Further in the same future(now 92), he has lost much of his weight due to his age and a steady diet of futuristic health food.