Characters: Both Fireboy and Watergirl are main characters who complement each other's strengths and weaknesses best. Fireboy also has to deal with addicts, and Watergirl would be better for the job at other times.
Fireboy has the ability to set fire and collect red diamonds. He is also slightly stronger than Watergirl. Water and green mood is its downfall.
Watergirl will walk on the water comfortably and collect blue diamonds. She is also quick. Firegirl's downfall is the verdant humor of the lakes of fire.