A Rebel grunt holding an automatic rifle, which they never use in the game.

Slightly resembles the .30 cal Browning Automatic Rifle.

From Metal Slug 1.

A female character. I guess she was suppose to be the character for those who chose to play as the first player.

From Metal Slug 1.

Another female character, this time the one that appears as the second player. She has a hair style that strikingly resembles that of Fio's, and she even wears glasses to go with it.

From Metal Slug 1.

Our old friend Satiko Suzuki, who appears in the first game's ending. Strangely, she seems to be walking a dog instead of praying in this picture.

From Metal Slug 1.

Early concept of Sophia Greenville. Note how she goes from cute to serious from left to right.

From Metal Slug 1.

Sophia in some sort of demonic dress. Touche.

From Metal Slug 1.

Unknown character #1. Slightly resembles Eri, but with shorter hair. Eri has long hair. This one doesn't.

From Metal Slug 1.

Unknown character #2. I couldn't determine the gender because A) there are glow marks on the cheeks, but B) no visible shading of boobs on the chest.

From Metal Slug 1.

Unknown character #3. I've given her the nickname of "Mechanic", because she appears quite a few times near Tank Slugs.

From Metal Slug 1.

Evil Marco in form of a dragon. Hehe.

From Metal Slug 1.

One of the game's creators, Andy, is drawn here by Max D. An incredibly geeky aura surrounds him.

From Metal Slug 1.

I assume that Max D. had too much time on his hands.

From Metal Slug 1.

An early concept of the Metal Slug 2's mutants in mission 5?

From Metal Slug 1.

The guy resembles Amadeus from Metal Slug 4, but this picture was drawn during the development stage of Metal Slug 1, with six years of gap in the time period between them.

From Metal Slug 1.

Robotic soldiers. How gentleman of him to have his pinky up like that!

From Metal Slug 1.

Destroyed Super Bio-boosted Soldier from the pictures above. Quite a gruesome scene that we have here.

From Metal Slug 1.

This must be the artificial heart that the SBS units use.

From Metal Slug 1.

I sometimes wonder what the concept artists were thinking when they draw pictures like these.

"Hey, can you spare me a grenade?"
"Sure thing!"
*plucks a grenade out of hair

From Metal Slug 1.

Another unknown character who remotely resembles Eri.

From Metal Slug 1.

I can't decided whether or not if this character is connected to the one in the picture above. But what I could determine was that she is evil. Evil enough to be have evil eyes, wear evil earrings and uniform, and stand in front of an evil-iciously lit background.

From Metal Slug 1.

Ragey's note: I've been emailed about three times saying this character bears a resemblance to Captain Harlock, emphasised in these images. I never quite saw the similarity, but if people keep telling me, may as well say.

We will never know who she is, but she has a marking scribbled on her forhead.

It reads, "metasura", which is a slang term in Japanese for "Metal Slug".

From Metal Slug 1.

Boob rockets with bandages covering the nipples. How cliche.

No idea on who the woman in the picture is, though.

From Metal Slug 1.

"Special Madams", they call her.

She looks as if she's about to shove that rocket launcher up someone's ass.

But in the game, however, all she really does is to act like... civilian, a non-combatant.

From Metal Slug 1.

Sergeant Allen O'Neil drowning in water.

We don't actually see him drown until Metal Slug 2. And this art is suppose to be part of Metal Slug 1's concepts.

Mrs. O'Neil.

Now you realize where Allen Jr. had come from, eh? Talk about Beauty and the Beast.

From Metal Slug 1.

Rumi holding an anti-materiel rifle. It would have been nice if she could be used as a combatant like Hyakutaro.

From Metal Slug 2.

Two new faces in this picture. One is a cute chibi girl running around with strange police uniform on that says "USPD", and another being a guy with a mustache wearing a fur hat made out of raccoon.

On the second look, the guy just has overgrown nose hair. Eww...

From Metal Slug 2.

Parker is a representative of a gaming company named "Duke", or some such. He travels around the world in order to promote his company's titles, whether the product be for children or grown-ups.

He carries around a briefcase packed with Neo Geo game cartridges, which your characters steal them for points every time it is spotted.

Yes, he does look quite alike Amadeus, doesn't he?

From Metal Slug 2.

Alien tentacle rape! Nah, I think it's more of a kidnapping of a poor Rebel soldier that happened to be sleeping by a Martian.

But the picture still does not look right, in my opinion.

From Metal Slug 2.

"Rise Above The Space"

Jeez. I wonder how their babies would look like.

But it's the horrid image of those two reproducing in a dimly-lit room that terrifies me the most.

From Metal Slug 2.

Major Margaret Southwood, your training instructor.

From Metal Slug 2.

Unknown training instructor #1. Could have been an earlier concept of Margaret.

From Metal Slug 2.

Unknown training instructor #2. Could have been an earlier concept of Margaret.

From Metal Slug 2.

Unknown training instructor #3. Could have been an earlier concept of Margaret. Her hairstyle is very similar to Margaret's, but is slightly different in a way due to the size of her sideburns.

From Metal Slug 2.

Sophia Greenville. I don't know how she got stuck in Metal Slug 2 concept art gallery.

I'm guessing that this is Meeher, one of the planners for the Metal Slug games when SNK was still around.

At least he's not mooning the viewers.

From Metal Slug 2.

An unused type of metamorphosis for the characters in Metal Slug 3. They are suppose to be evil.

From Metal Slug 3.

Our heroes enjoying their vacation at the beach.

It's just too bad that we don't have much more pictures like this.

From Metal Slug 3.

From left to right;

Chris, Hyakutaro, and Rumi.

I couldn't read out Chris's last name because of the poor resolution that the manual was scanned in, and the fact that I was too lazy to find the box that contains the damned thing.

I don't know about Chris, but the really freaky thing about those characters is that they were listed up in the Playstation editions of Metal Slug 1, on page 27. But you never see them in the actual game.