- Full Name: Theo Johnathan Casey
- Race: Ornaran Terran hybrid
- Age: 30
- Place of Birth: Ornara (Delos III)
- Gender: Male
- Telepathic Status: T/E0
- Height: 6'1
- Hair Color: Black
- Length of Hair: Short
- Eye Color: Hazel
- Skin tone: Slightly Pale
- Birthmarks, Scars, Tattoos: None
- Build: Athletic/Muscly
- Taste in clothing (Off Duty): Anything that comes out of the draw first.
- Voice: Isn't deep enough to be called deep, but is a low tone.
- Hand: Right
- Favorite Room: Wherever a Double-Handed Grip Type Four Phaser Rifle is.
- Habits: Talks back to superiors depending on his mood. Although it doesn't happen often.
- Ambitions and Goals: To collect all six phaser rifles from the 2260s to the 2370s.
- Older Sister: Kelly Casey
- Not much is known about her. It is presumed, by the way Casey speaks of her, she was addicted to felicium.
- Marital Status: Divorced (once married to Nick Falls)
Nicholas, otherwise known as Nick, is a joined Trill. The previous Falls was female - Stace Falls, of whom Casey knew very well. Nick confessed that Stace had a crush on Casey, but never said anything or drew attention to it.
The relationship between Nick and Casey started soon after the accident that took Stace's life, but the symbiont survived, and was transferred to Nick. Nick revealed a lot of things to Casey about Stace. There was the unfortunate possibility that the relationship between them may have been influenced by Stace's feelings for Casey, and not Nicks. They finalized a divorce in late 2395.