Metal Slug firsts by Faction

Here's the list of first introduction in Metal Slug series by faction.

Regular Army

• First male protagonist: Marco Rossi
• First 2P male appears as a selectable character: Tarma Roving (Debut in Metal Slug 2/Metal Slug X)
• First female protagonists Eri Kasamoto and Fio Germi (Debut in Metal Slug 2/Metal Slug X)
• First SNK protagonists to appear in Metal Slug games: Ralf Jones, Clark Still, Leona Heidern, Heidern, and Whip
• First Drill Instructor to have an in-game sprite: Sophia (Debut in Metal Slug Attack

Rebel Army

• First main antagonist that appears as a boss: Donald Morden
• First major antagonist appears as a sub-boss Allen O'Neil
• First female Rebel Army member: Abigail
• First experimental soldier: Vita
• First scientist to work for the Rebel army: Navy
• First character to have a personal vehicle: Rapid
• First conscripted infantry: Huracan