Near the end of the film, he appears from a gigantic drill vehicle to show his existence, prompting the Parr family to spring into action and serving to demonstrate that they will go on to have many adventures and fight various enemies as a superhero team.
The Underminer appears in a flashback by Tony Rydinger, in which he is saying his famous quote, in which Tony runs away and hides under a car from him. He is also booked as a Terrorist and Bank Robber, which were not present traits in Rise of The Underminer, released 13 years before.
The Underminer uses a vacuum to suck up money from the bank in which Mr. Incredible tries to prevent him from doing so, after being sucked up into the machine. He breaks out, and tries to fight Underminer, as he sets off bombs to destroy buildings above.
He later escapes with the stolen money, leaving his machine to knock down the Town Hall, which Frozone barely prevents from doing so. Afterwards, it is unknown what happened to the Underminer since he is never seen again afterwards and only mentioned a few times more (such as the part where two detectives question Mr. Incredible and Elastigirl to know if they stopped the Underminer from succeeding his mission to which Mr. Incredible explains that his family failed to do so). However, during the credits, the Underminer can be seen in his drill machine coming up off of the ground.
In the comic series, The Underminer makes an appearance in the "Terror from Beneath" story arc, in which he briefly allies with Dash to fight off alien invaders. However, the appearance is revealed to be part of an extensive hypnosis-induced dream. He later makes an actual appearance as a member of the Unforgivables, the criminal alliance headed by Xerek. As part of a plan to ruin the reputation of the Incredibles, Underminer is given control of a giant robot painted in the Incredibles' colors and rampage through Metroville. Xerek later eliminates Underminer upon completing his purpose.
- The Underminer (in keeping with the tradition of having most of the cast be based off of Marvel characters), is likely based on the Mole Man who was the very first known villain of the Fantastic Four.
- The Underminer was planned to appeared in Disney INFINITY but was scrapped and only was seen in concept art although he does not actually appear in the game. However, customizations for buildings based on The Underminer can be unlocked in The Incredibles Playset.
- The Underminer was intended to appear in Disney INFINITY: 2.0 Edition according to concept art.
- The Underminer has two robotic hands. They are very articulate and have two webbed like fingers and one thumb on each hand. Whether these are used as mining equipment (As the appearance of them resemble something used for excavating), as weapons, or as prosthetic replacements are currently unknown.
- The Underminer is one of the few Disney or Pixar villains to succeed in his goal. He manages to rob a bank and escape with all of the money and is never caught afterward.
- He is the second Incredibles villain (after Bomb Voyage) to not be captured by the hero and is able to get away with a crime (both instances involving bank robbery).
- Much like Syndrome, the Underminer does not have any actual superpowers, instead utilizing his inventions to cause chaos and wreak havoc on the world. This is proven when Underminer tries to fight Mr. Incredible in hand-to-hand combat, but the latter is easily able to throw him across the room.
- The Underminer scene originally went through many changes during the movies’ development, but they were all scrapped in favor of the runaway tunneler. The scene was originally going to have giant clay golems bursting out of the ground, robots, giant earthworms, and even human miners. The human miner idea eventually had a half-life in the LEGO Incredibles game.
- The Underminer is the only villain who appears in all the two Incredibles movies.