Derek Jupiter is the Lead Singer of Iron Weasel. Unlike the other members of Iron Weasel, he is from England. He is shown to be arrogant, cocky, selfish, and narcissistic but usually is fairly charming. Derek is a very skilled magician and can speak Spanish,Turkish, and Japanese. In Magic Tripp, he refused to let anyone touch his prized motorcycle, and smashed a tennis racket over whoever touched it. He is shown to have a fear of snakes, but he got over it in the episode Spiders, Snakes, and Clowns. As mentioned in What Happened?, Derek owns a dungeon, in which he keeps the keys to in the toilet until Ash found them, and became nervous when Tripp asked of it. Derek owns a jacket made of pure gold, as seen in Money Bags.
- He delivered a baby, named Derek Junior (by him).
- Is a skilled magician, but after a traumatic experience, refused to do so for a long time. However after "Magic Trip", he started performing tricks, every so often, as seen in "Prank Week" and "Chucky's Revenge" He also performed several in Burning Down the House.
- Can play Guitar as seen in a few episodes. He can also play a keyboard.
- He once blew 10 million dollars in a day by paying for a $10 cab ride and leaving the rest of the money in the back seat.
- He started Iron Weasel.
- Can speak at least four languages (English, Spanish, Turkish and Japanese)
- There is two things that easily make him angry, insulting his voice, and impersonating his accent, as he said in Bleed Guitarist "no one steps on the Queens tongue".
- Next to Tripp, he seems to be the smartest.
- He is a very good artist.
- He wrote a book called, "Derek Jupiter: The Smartest Guy in Iron Weasel" but spelled Smartest, "Smartist".
- He is the tallest member of Iron Weasel.
- He had a fear of snakes, but overcame it in Spiders, Snakes,and Clowns.
- Has a fear of cutting his hair.