Firestorm Girls

The Firestorm Girls are the 2nd Dimension counterparts of the Fireside Girls. They are a branch of The Resistance, led by Isabella Garcia-Shapiro.

Foundation
The circumstances of the Firestorm Girls' founding is unspecified, nor is their purpose in combat against Doofenshmirtz. However, they seem to be a highly-trained elite unit, whose known troop is troop 46231.

The 1st Dimension
The Firestorm Girls have a small cameo in the movie. They capture Phineas, Ferb, their 1st Dimension counterparts, and Buford, but they release them under the command of Isabella. They are later responsible for the arrest of Doofenshmirtz upon his return to the 2nd Dimension ("Phineas and Ferb The Movie: Across the 2nd Dimension").
 * Isabella Garcia-Shapiro (2nd Dimension) (Troop Leader)
 * Gretchen (2nd Dimension)
 * Holly (2nd Dimension)
 * Milly (2nd Dimension)
 * Ginger (2nd Dimension)
 * Adyson Sweetwater (2nd Dimension)
 * Katie (2nd Dimension)

Outfits
The Firestorm Girls uniform has a standard color of a silver shirt, a dark-green beret on their heads, brown straps worn over their left shoulder that appear to store rolled-up strips of paper, brown pants (with the exception of Gretchen), and black shoes. However, identical to the Fireside Girls members' clothing, every one of the girls' uniforms has a personal touch. The girls look similar to when they were in the video Isabella had when Candace asked her for any unusual video. ("Phineas' Birthday Clip-O-Rama!")
 * Isabella's uniform is a silver shirt with torn sleeves, black pants with diamond-shaped patches on the portion that covers the kneecaps, black shoes, gray gloves, her beret has a light-green bow on it, and, unlike the other Firestorm Girls, she has a badge with a green circle at the center, with a red lightning-bolt insignia crossing it (probably the Firestorm Girls symbol).
 * Gretchen's uniform has light-green pants instead of brown, and said pants are tucked in.
 * Holly's uniform also has her shirt tucked in.
 * Milly's uniform also has her shirt tucked in; plus, her beret features an extension coming from the front and her shoes are the most lightly-colored out of the troop.
 * Ginger's uniform has diamond-shaped patches on the portion that covers the kneecaps, like that of Isabella's pants, and her beret seems to slightly sag down to the front.
 * Adyson's uniform has her shirt sleeveless and, as with Isabella and Ginger, diamond-shaped patches on the portion that covers the kneecaps.
 * Katie's uniform has her shirt tucked in.

Trivia

 * The troop's name was never mentioned in the movie.
 * Gretchen is the only Firestorm Girl that speaks in the movie besides Isabella.
 * Milly-2 didn't appear with the others when Doofenshmirtz-2 was arrested.