Augustus P. Crumhorn the fourth is a brilliant billionaire industrialist and the "Daddy" of Princess (Dawn Crumhorn). He is an occasional antagonist of Danger Mouse who's secretly biding his time to, through his companies, rule the world. He is voiced by John Oliver.
Crumhorn is a thin doberman, with the typical black and brown color scheme. He clothes consist of a blue shirt, red belt, black pants, and a pair spectacles.
Crumhorn IV, is an manipulative, cunning, corrupt business man out to claim the world as his own. While initially coming of as calm, nice, and collected, anyone who's met him would say otherwise. He has no qualms with enslaving the entirety of humanity, destroying hospitals for no reasons, and even murdering his allies if it means success.
Though it does appear he has a soft spot for Dawn Crumhorn (The Princess), as he spoils her with whatever she could want and he does seem genuinely fatherly towards her. Even after she inadvertently ruined his scheme in Mousefall, he still wished her the best as she was his daughter. Still though this doesn't mean he won't get upset with her if she throws a fit or becomes to much of a hassle.
While he is an egoist, he's fairly secretive about his agenda. Unlike someone like Greenback, who's fairly open about being evil, Crumhorn prefers to work from the shadows, hence why he didn't appear until the Season finale. He even got upset with Ian and called him an idiot when he put the Crumhorn label on literally everything in the world, as he doesn't want anyone to know what he's scheming until it's to late for his victims.
- Despite only appearing fully in Mousefall (episode 50), he is in numerous of the episodes before, mentioned, referenced, or his company logo is there. His inventions, Spamchops and Giraffe Warriors are also on previous episodes.
- In the episode Mousefall, it is mentioned how Crumhorn created Giraffe Warriors game, however in a previous episode Queen of Weevils, the Queen of Weevils says that "In the time of the ancients, we only had Giraffe Warriors 2." It is nowhere implied or mentioned that Crumhorn has been around for over 1000 years, so how could he create it? Well, this is a possible theory: he just created Giraffe Warriors 7. When he says he created Spamchops, it comes up with Penfold's Spamchops account, and when he says he created Giraffe Warriors, it comes up with the poster for Giraffe Warriors 7. It may be revealed he travelled back in time, but the only way to do that is with a time machine, which only Isambard King Kong Brunel has. However, since Crumhorn owns lots of things, he may own the Time Machines. We may find out in future episodes.
- It's implied that, similar to how agent 58 is the son of agent 57, that Doctor Augustus P. Crumhorn IV is the son of Doctor Augustus P. Crumhorn III
- He's the second villain with a daughter who also happens to be a villain, the first being Greenback.
- Though Crumhorn's daughter was introduced before Greenback's daughter, Crumhorn himself wasn't revealed to be a villain until after both Greenback's and Delilah's debut.
- He claims in MouseFall that he created Giraffe Warriors, thought the centuries old witch, The Queen of Weevils claims that Giraffe Warriors has been around since her youth in her debut "Queen of Weevils" (episode).