A typical shounen Tournament Arc series, save that it's done by CLAMP (and was, incidentally, their first series directed at a male audience), has a predominantly female cast without being a Bishoujo Series, and involves fighting dolls controlled by the player's mind.Suzuhara Misaki is the new girl at Eriol Academy, living with her aunt Shouko in Tokyo after growing up with her grandparents. Her mother, Shuuko, has been so busy with work in Tokyo that Misaki hasn't seen her since she was five years old, but she refuses to feel sad about it or look into her mom's whereabouts, feeling that she'd be a burden. Upon arriving in Tokyo, she sees a crowd gathered around a screen playing an intense match between two fighting dolls, called Angels, in a game called Angelic Layer. With some persuasion from a Mad Scientist, Misaki jumps at the chance to get her own Angel and start competing nationally.Besides the twists to the formula, Angelic Layer starts out like a regular shounen adventure series of the same mold. Misaki meets new friends, begins to fight and realizes that she has a vast, incredible talent for the game. All the while, the Mad Scientist Icchan is watching her progress in the tournament, revealing to the audience the reason that he cares so much about Angelic Layer and about this particular little girl.The manga treats certain plot elements completely different from the anime, which also makes big changes to the battle system later on. Either is recommended, as while the anime's changes make more sense later on, the manga is still quite good.Angelic Layer is either an Alternate Continuity or prequel to Chobits and Kobato.It is also notable for being one of the first Shounen series to innovatively break genre conventions and feature a female leading protagonist, a trend which eventually caught on and appeared in franchises such as Chrono Crusade and Soul Eater.Despite the very similar premise, no relation to Custom Robo, which first appeared a mere six months after the Manga.
Butt Monkey: Ogata, Iccan's subordinate. The things he is "penalized" for are rarely his fault, though Icchan never seems to care.
Calling Your Bathroom Breaks: Tamayo does this a couple of times early in the series, usually to show that she's still pretty childish. As she matures over the course of the series, she eventually stops.
Cannot Spit It Out: Icchan, toward Shuuko. Eventually, he manages to confess his feelings, even going as far as asking her to marry him. We never hear her answer.
Catch Phrase: Misaki's "Naaa!" whenever she gets surprised, and Icchan's "Icchan nyoro!" whenever he's trying to surprise Misaki.
Companion Cube: The Angels. They may seem like Mons at first glance, but the whole point is that they're really just dolls who can only move on the Layer. Shuuko points out that treating one's Angel as a Companion Cube is required to fully enjoy the game.
Continuity Nod: The various one-shot characters who Misaki faces over the course of the series all show up as spectators to the final fight between Athena and Hikaru.
Cool and Unusual Punishment: Icchan's subordinate Ogata often gets penalized for things that go wrong, with punishments including making him eat spaghetti through his nose and dropping a live octopus down his pants.
Curb-Stomp Battle: Pretty much any fight that Misaki isn't in. Or isn't between two supporting characters (see Spoiler Opening below. Especially if Athena is involved).
Explosive Overclocking: Kaede's Angel Blanche and Sai's Angel Shirahime both have "Hyper Mode", which maxes their power but risks destroying the Angel's core components permanently the longer it is used. In the manga, where only Blanche has the capability, it's risk-free.
Hair Colors: Surprisingly, most everyone has realistic hair colors, with examples like Ringo's being justified in that she's an Idol Singer. Only the Angels have really unnatural hair shades, but they are dolls after all.
Invincible Hero: Misaki only faces one major loss in the entire series. Jusified in that the series itself takes place during a single tournament. When she lost, the tournament was at a stage were losing didn't immediately result in elimination.
Serious Business: Subverted. There are a number of Dei who treat Angelic Layer as Serious Business, but according to a number of characters, including the man who invented the game itself, they're doing it wrong and should just be having fun.
Shipper on Deck: Tamayo apparently thinks this way about Misaki and Koutarou.
Hikaru is actually based on Shidou Hikaru, the heroine of Magic Knight Rayearth; also, Eriol Academy is named after Hiiragizawa Eriol from Cardcaptor Sakura. Plus the manga has newspaper clips of how the CLAMP School Detectives have vowed to investigate the disappearance of three girls from Tokyo Tower (Another Rayearth ref.)
There are also two points in the manga where Misaki is shown singing the anime theme tunes for CLAMP School Detectives and Rayearth season 2.
Shrinking Violet: Shuuko. In the manga, this is more or less the reason why she left Misaki.
Spoiler Opening: The opening contains clips of the final climactic battle. Also, if you want to know if Misaki's current opponent is just a one-shot character, or has a bigger role in the story... if they don't show up in the opening, they're a one-shot.