Ami is the brains of the outfit, possessing a very high intelligence (It's said to be over 300 IQ, but that's gotta be a usual Anime over exaggeration). Though she truly does have great intelligence, most of her great mind is "book smarts" rather than "street smarts". She spends much of her free time studying various disciplines and staying ahead of her class. It's her desire to be the best of the best in school to achieve her dream as a great physician that makes her look more like a genius. Ami-chan is also highly competitive and cringes at the sight of someone matching or even beating her test scores, prompting her to push herself much harder. This trait is most prevalent in the first season (with Urawa) and in the Ami-chan special (with Mercurius). Her constant studies and competition with other geniuses, though, leaves her little room for a social life of any kind. Ami has very few friends, and is often looked at by her classmates as an arrogant genius who basks in that high intellect of hers (She's too damn good looking to be seen as a nerd or a geek).

This is true until, of course, she meets Usagi and the rest of the Sailor Senshi. Since the first day she met Usagi, she has slowly begun to crawl out of that rather shy and withdrawn shell of hers. A couple of such examples are her spying on Usagi and Mamoru in the Sailor Moon R movie and her starry-eyed gawking at the Three Lights in Sailor Stars (she was one of the first members of their fan club).

Throughout the series, her personality transforms from the shy girl always studying and having little to do with people into a more outgoing, social, and still studying a lot type of girl. One of her personality traits that never die out in her is the fact that she's reluctant to admit to anything contrary to her academic tendencies, such as celebrity fandom, the cute guy in her class, the latest fashions, and even her skills at video games.

As Sailor Mercury, her swift and intelligent mind does much of the work, which makes up for her rather weak attacks. Her attacks, however, are the most versatile of the Senshi's. Her "Shabon Spray" alone has a number of uses, from freezing, to attacking multiple enemies, to fogging up a place, and even cooling the heat of a raging inferno. This versatility more than makes up for the rather low brute force of her powers (that honor goes to Sailor Jupiter). However, she does get a more offensive attack in Sailor Moon SuperS, "Mercury Aqua Rhapsody". She also uses a visor coupled with a minicomputer to gather data, see through illusions, scan for weaknesses, and basically give her and the Sailor Senshi what they need to ensure success in battle.

Whether in school or in battle, you can count on Ami to come up with some good strategy to get you out of any fix, yet still get some eyes popping just from her beauty alone.

Mercury Power, Make-Up

Sailor Mercury's first transformation. She receives this at the beginning of the Sailor Moon first season. 

Mercury Star Power, Make-Up

Sailor Mercury's second transformation. She gets this in the second half of the Sailor Moon R season after receiving the Star Pen.

Mercury Crystal Power, Make-Up

Sailor Mercury receives this transformation from Pegasus in the Sailor Moon SuperS season to become Super Sailor Mercury. 

Shabon Spray (Mercury Bubbles Blast)

Her first and most common attack. She forms a bright blue ball in front of her, spins around with it, and waves her arms out, sending many bubbles at her enemy. This is also her most resourceful attack, the fact that she uses it for just about anything. She's even used it to protect her from the heat of the DD Girl's fire at the end of the first season.

Shabon Spray Freezing (Mercury Ice Bubbles Freeze)

She gets this attack at the beginning of Sailor Moon R. This is a rare attack and another variation of Shabon Spray. This attack freezes her opponents on contact.

Double Shabon Spray

Another powered up version of Shabon Spray she uses in Sailor Moon R. She often uses this variation to attack multiple enemies.

Shine Aqua Illusion

This is a more powerful attack than any of her Shabon Spray attacks. A drop of water forms, then Sailor Mercury spins around gathering the water from a pond below her. She then flings her arms forward sending jets of water at her opponent, often freezing them.

Mercury Aqua Rhapsody

Sailor Mercury gets an even more powerful attack in the Sailor Moon SuperS season after receiving the power from Pegasus. As she says "Mercury...", the sign of Mercury with a harp in the background appears on her hand. Then, she plays a crystal harp, sending many powerful jets of water at her opponents.

Mercury Aqua Mirage

This is Sailor Mercury's one-time attack she uses in the Ami-chan special. Simple, yet powerful attack, she sends a huge ball of water at her enemy, often taking it out with one shot.