- Complete Monster: Ajo. A former Japanese Imperial Army officer turned Corrupt Corporate Executive, he forcibly extracts the object-animating gel out of humans and has no care for human lives except as resources, eliminating anyone who stands in his way regardless of them being harmless civilians, children, or elderly and condemning others to a Fate Worse Than Death just to feed his monomaniacal obsession with creating working Ridiculously Human Robots. Ajo repeatedly crosses the Moral Event Horizon, due to his mistreatment of Miho, and especially his savage beating of her replacement, Beniko.
- Crowning Music of Awesome- Key's Lullaby. Also counts as a Crowning Moment of Heartwarming for many.
- Jerk Sue: Tsurugi. He's a director, producer, dancer, choreographer, author, screenwriter, voice coach, and incredibly abusive. Possibly a deconstruction because people close to him come to realize his abuse. Oh, and because he's batshit insane.
- Les Yay: Key and Sakura.
- Moe: Key is another pre-Neon Genesis Evangelion prototype of applying this trope to an Emotionless Girl.
- Moral Event Horizon: Ajo's treatment of Miho, and especially his savage beating of her replacement Beniko.
- Seinfeld Is Unfunny: When this show first came out, it was regarded as the biggest Mind Screw in the history of anime. Today, when you compare it to some of the shows that take after it, it doesn't seem convoluted in the least.
- Tear Jerker: Sakura's death.
- What Do You Mean, It's Not for Kids?: Do NOT be fooled by the show's premise of an android girl seeking to make 30,000 friends in order to become human, and think this is meant for the kids. Seriously. Don't.
- Woolseyism: (End of series spoiler.)During the massive infodump in the 14th episode, Wakagi uses the word "omoi" — Japanese for "thoughts", "feelings" and so forth — to describe the substance Ajo referred to as "Gel". The Viz translation uses the German word "Geist" ("mind", "spirit", and/or "ghost"), which helps get the point of it being Life Energy across.