Big Penfold is the 12th episode of Season 1 in the the Danger Mouse 2015 reboot.
Professor Squawkencluck makes a growing/shrinking invention to save the world from a meteor attack. When Penfold is accidentally turned huge, trying to stretch his trousers after they got shrunk in the hot wash, DM figures out it could actually be helpful to save the world.
We open on the earth, with a timer on it. Set for 3 hours we learn that when the timers up a meteor will crash into and destroy the earth. In a last ditch effort to save the earth the worlds greatest scientist have all come together in hopes of hatching a plan to stop it along with the world's greatest secret agent. Shortly after Danger Mouse and Penfold arriving a scientist named Isambard King Kong Brunel is called up to present his idea's to stop the meteorite. He first present a ginormous car wash to clean the meteorite (and not stop it). When this was met with a less then enthusiastic response, he pitched his "Asteroid Router", a devise that could maneuver the Meteorite, though not strong enough to move away from the earth. After this pitch his fellow scientist starting booing at him, reluctant to step of the stage Brunel pitched one last invention, "The Mold" which would be able to pin point the meteorite exact location. This resulted in Professor Strontium Jellyfishowitz (who was leading the meeting) to forcefully grab Brunel with his tentacles and lift him off the stage (and zap him a bit). Afterward Strontium called up Squawkencluck upon the stage where she pitched her "Shrinkatizer"'
Squawkencluck explained that her Shrinkatizer has the ability to both shrink and enlarge things at the expense of having to charge for 3 hours in between uses. She planned to use the shrinking option to shrink the meteorite to a size so small that it wouldn't do any damage. Her fellow scientist and Professor Jellyfishowitz loved this idea, though Brunel thought it was rubbish. Though Squawkencluck herself was unwilling to get close enough towards the meteor to set it off herself so she and the worlds head scientist choose Danger Mouse. Though Squawkencluck warned Danger Mouse to be careful, only for Danger Mouse to dismiss her claims by telling her that his invention was in good hands, only to toss it towards Penfold who drop the Shrinkatizer causing it to go off and shrink Jellyfishowitz's glass tank, causing him to let go of Brunel. While Squawkencluck and Danger Mouse we're busing attending to Jellyfishowitz, Brunel was quick to nab the Shrinkatizer and ran off, much to Danger Mouse's dismay.
Taking off on his steam power Pogo stick, Brunel hit the streets, though was soon on hot pursuit by Danger Mouse and Penfold. He was quickly apprehended, and when questioned on why on earth he would steal the earth saving devise, he claimed he wanted it to use it to make himself taller, and followed it up by saying they still had 3 more times to use the devise before the meteor hits. When hearing this Penfold asked if he could be allowed to use the enlarging option on his trousers which shrunk in the wash. Danger Mouse sarcastically replied with, "Of course, why don't we all have a go?" only for Penfold to take him literally and use the enlargement ray on his pants, though he inadvertently shot himself and grew to huge proportions.
Both Danger Mouse and Brunel watched in awe as Penfold became huge, and began to panic. Danger Mouse rushed to the Mark 4 to calm down the huge Penfold. Meanwhile Brunel noticed the Shrinkatizer in the trouser leg of Penfold pants. He attempted to warn Penfold and Danger Mouse of it's location but was apprehended by the Mark 4's claw before he finished his sentence.
Danger Mouse while concerned for his friend, decided that the Meteorite came was his first priority, so he told Penfold to go wait in the ocean, as he thought he wouldn't be able to do any harm there. With an hour and 30 minutes left til the meteor hit, Danger Mouse prepared to stop the meteor, only to realize he doesn't know where it is. He then pulled Brunel out of the Mark 4's trunk to ask if he's seen it. He then informs him that it's located in Penfold's trouser cuffs, only for both of them to realize Penfold's gone.
Unclear on how to find Penfold, Brunel suggest they use his mold devise to help find Penfold. Pressed for options, Danger Mouse agree's, only for his devise to take them to an iceberg. after 40 minutes of searching Brunel's devise finally finds Penfold at a remote island. In a hurry, Danger Mouse warned Penfold that the ray was in his pants. Penfold then told him that his friends where trying to straighten out his clothes. He introduces his friends,Tyrannotour-bus Rex, Frankenstein Rooster, which Brunel revels himself to have created, though it seems his creations aren't to fond of him as they began to chase him. Meanwhile Anacondles was trying to stretch the trousers the size changer ray flew out of the pants, hit Brunel in the head and zapped Penfold.
While growing he also crushed the shrink ray, now making shrinking the meteor an option. Danger Mouse tells Penfold to catch the meteor instead. While hesitant, out of fear he might mess it up, he ultimately catches the meteor. Afterward, Brunel finds the crushed size changing ray and attempts to use it on himself, only for it to backfire and shrink him instead. He is then pursued by his tyrannotourbus-rex, meanwhile Squawkenclucks and Danger Mouse are enjoying some coffee as they give their comments on today's adventure, as Penfold is being shrunk with Brunel's ginormous car wash, and with that the episode ends.
- Richard Osman stars in this episode as Professor Strontium Jellyfishowitz.
- This episode marks the official debut of Isambard King Kong Brunel, who would later go on to become a reoccurring villain.