Helium is the second playable character in the Atomic Series and is Hydro's bubbly and optimistic girlfriend. She was the one who found Hydro and took him in after he saved her from marauding alley hoodlums. Even though she has quite an odd personality, she's also very headstrong and sticks to her decisions. She's always looking out for her friends and takes their well-being and concern into consideration. This may be the reason why she even signed up to be an agent along with Hydro, so he wouldn't have to worry about saving her again!

Helium plays the damsel-in-distress role…..for a bit. It’s not until after Hydrogen frees her and returns her umbrella that she becomes a playable character herself for the duration of the game! Helium specializes in long-range combat, using her umbrella as a machine gun (Penguin style) to shoot down her enemies without even having to touch them! The side-effect, however, is that the enemies won’t be stunned by her attacks, so Helium will have to be careful, especially with her low defense. To make up for that low defense, she’s practically the lightest character in the game, being able to jump higher than anyone else and then float back down using her umbrella. For the latter, she can whip out a ray gun that she keeps hidden in her hair to continue shooting enemies while floating. Some enemies will grant her a power-up for her weapon, be it rapid fire, lasers, or even the scatter shot, Contra style!