Nick Fury is the S.H.I.E.L.D. director and the one who assembled the Avengers, and now the Mysterious Five. He is serious and level-headed, and is quick to stop any threats coming into the Mysteriousverse.
Iron Man, also known as Tony Stark, is the leader of the Mysterious Five Organization. Usually calm, but can sometimes be a bit cocky. He has several suits that grant him different abilities.
Dexter is the second-in-command of the Mysterious Five, and a child prodigy with his own laboratory. While he is arrogant and self-obsessed most of the time, he respects his allies deep inside. He views Tony Stark as a role model, kind of an "older brother", and hopes to become a wealthy businessman like him. Tony acknowledges this, and gives him his own Iron suit.
Inori Aizawa is an expert on many things, due to a PC-based microchip being implanted in her brain. As such, she can use Internet Explorer to search up anything that no one else understands, not even Dexter or Tony Stark. Inori can even enter computers and walk through the Internet. She thinks Dexter is okay as a member, but wishes he would stop boasting so much. Occasionally headstrong and overeager, but will fight to the end.
Chuck D. Head
Chuck D. Head is a monster body with a human brain. The "monster" side of him leads him to jump to conclusions, but he doesn't really notice, and continuously lectures Emmet about doing the exact same thing. He has known Inori since the days they lived in the same apartment, and they seem to be good friends. Chuck thinks Dexter is a bit of a "nerd", and gets bored of his overemphasis on the details; however, he is usually quick to assist him with supernatural stuff.
Emmet used to be normal, a little too much. But after realizing his potential as a Master Builder, he became a hero with a strong sense of justice and peace. Being a Master Builder, he uses LEGO bricks to construct anything he can think of. He thinks his fellow Mysterious Five members are "awesome", in their own individual ways.
Hawkeye is the leader of the Mysterious Five Task Force, which works in the city to keep organized crime out.
Wyldstyle, a.k.a. Lucy, is apparently Emmet's girlfriend. She is a skilled Master Builder, and seeks to guide Emmet throughout his Master Building career.
E-123 Omega is a robot originally designed by Dr. Eggman, but Mandark reprogrammed him in The Mysterious Five Project to eliminate Dexter and Tony Stark. Dexter reprogrammed him again, and he is now a member of the Mysterious Five Task Force.
First Knight of the Chozo Order, Dame Samus Aran is the leader of Sea Goddess Palutena's underwater army in Seaworld, but she briefly joins the Mysterious Five Organization to stop Bill Cipher in Binary Time.
Peter Cipher, unlike Bill Cipher, is a serious, rude and direct-to-the-point character. He often alludes to being a human in the past, and Bill Cipher having to do with his transformation to a demon. It is due to this that he doesn't like to associate with others and he lives a lonely existence. However, he still retains pride for his name and won't let himself die under any circumstances.