Alex
Alex has short black hair and dark skin. She wears a yellow spy suit. Although she is the fitness junkie of the group, Alex is very clumsy and sometimes can be a little slow or naive, but she is the toughest of the spies. This sometimes hinders the girls on missions and causes them to get into a worse predicament then what they were already in. She tends to act on impulse and does not think about what she is going to do which can be a problem at times. Alex is the sweetest and kindest of the three and always puts her friendship with the girls first. Despite being the most athletic, Alex is the second "girliest". She is very concerned with fashion, boys, and her looks, though not to the same extreme as Clover. She is the most childlike and the youngest one of the group.

Alex often serves as a link between Clover and Sam who often have squabbles. Sometimes she takes to Clover's more "girlier" side (usually having to do with fashion and sometimes boys), or she will join forces with Sam (usually having to do with Clover over-reacting or acting airheaded). Sam and Clover often have meaningless fights over who is the closer friend of Alex's.

Alex is well known for being a bad driver. (Ironically, in the episode "Aliens" it looks like Alex passed her exam with flying colors, but in the third-season episode "Space Much?" she admits she barely passed driver's ed). Not only does she drive a car poorly, this inability apparently applies to any type of vehicle. She tends to drive very fast and a little out of control which leads to her not driving as much as the others.

It is revealed in "Alex Gets Schooled" that she is a mix of Caucasian and Hispanic. She was originally thought to be of Latin-American heritage. Alex's running gags are her clumsiness, bad luck, and being frequently kidnapped.

It is often said Alex's last name is Vasquez. However, the show's creator says this is not true and is only a rumor.

Alex was voiced by Katie Leigh in seasons 1-2 and Katie Griffin in season 3-present