As an alien, Allan was the more practical of the two, thinking before acting. He would play his reed flute to summon a cardian, and almost always let Ann pick the cardian. The only time he picked the cardian for himself, the cardian went crazy and started attacking everyone (not the people he told it to attack).
As a human, he was followed around constantly by girls for his good looks. When he first saw Serena, he immediately fell in love with her and vowed to make her his.
As an alien, Ann was the more aggressive of the two, usually acting before thinking. She picked the cardian for Allan most of the time.
Ann went to Serena's school as a human, and was in her class. She went under the name Ginga Natsumi in the Japanese version. The first time she saw Darien, she immediately fell in love with him, and constantly competed with Serena to win his heart. Serena tried to become friends with Ann also, but Ann would usually treat her like dirt (which got her friends a bit mad). Her reason for this was because Allan liked Serena, so Ann would get extremely jealous (even though she chased after Darien and made Allan jealous).