Nadia is a recurring character introduced in Metal Slug 4.
"This is suh-sweet, non?" - Nadia's pet phrase
Nadia dreamt of becoming a supermodel, but could not resist eating. She kept on eating and gaining weight. She then enlists in the Regular Army, despite her modelling manager's plea, to keep the weight down, and succeeds in doing so. However, she finds a true potential for being a soldier and transfers into the S.P.A.R.R.O.W.S to gain combat experience. The operation against the Amadeus Syndicate was her first combat assignment. When it all ended, she didn't want to leave her new exciting life, so she inscribed into the Regular Army's Secret Services to continue working as an agent.
Nadia plays the same as any other character, although she uses a high-voltage Taser as her melee attack. Due to an in-game bug, she earns less points when using it.
Nadia cameos in the game's POW list, but she finally becomes a playable unit in a later update. She uses her taser as a close range attack and a Heavy Machine Gun that shoots Vulcan ammo as her long range attack. Her special is deploying a Walking Machine that starts on the base and crawls up to her. Once she's on the Slug, she fires Vulcan ammo as her normal attack and throws a Molotov as her special.
In 1.42.0, a special version of Nadia wearing a Valentine's dress, called Valentine Nadia, appears as an event unit. Her taser is replaced with a chocolate covered whisk, and her special has her tossing various explosives disguised as chocolate boxes.
Nadia is a primary unit in this game, which now re-establishes her and Trevor as part of the main cast. Units of her can be earned by the Daily Login or by the POW Shop. Her Valentine's Day form also shows up as part of the "Chocolate of the Dead" event as a pre-acquisition unit, now able to toss a small batch of boxes as a counterattack. In the event's story, she's protecting her chocolate from a horde of zombified Tarmas and Trevors.
A new version of Nadia wearing a skin-tight spy suit is introduced in the "Code: Assault" event as a VIP Crank unit (now an Event Crank unit). She uses a Submachine Gun, calls a modified Walking Machine, and tosses floating bombs as her special while on the Slug. Special Nadia, as this version is called, makes no appearance in the event's story.
Another variant called Everlasting Nadia has her in a striped bikini. Aside from stronger attacks, she can immediately deploy on top of the Walking Machine when skill 4 is unlocked.
Her zombified form has a new sound effect to mimic the ones used in Metal Slug 3 (she originally had an echoed scream rather than a gurgled one).
Nadia appears as a playable unit. She deploys by long jumping and firing from her pistol; her special is tossing a grenade. A summer variant called Brainwashed Nadia instead teleports into the battlefield and tosses explosive watermelons. Nadia was kidnapped and brainwashed by the Martians while sunbathing and was put into the Another Force.
In their idle animations, Nadia eats a piece of chicken while Brainwashed Nadia eats an entire slice of watermelon (including the rind and skin).
- The animation of Nadia eating a piece from a candy bar is unused in Metal Slug 4. It is restored in Metal Slug Defense and Metal Slug Attack.
- Tyra is a sprite edit of Nadia, who also is an edit of Eri.
- Nadia is the first female character in the series to have her own custom melee attack; the Stun Gun. This weapon is also used by Madoka in Metal Slug Attack.