— Stanley's personal motto, Dr. Stone, Chapter 153
He is the one who initially assaults Senku's group once they disembark on the territory of the United States. Once Xeno has been captured by the Kingdom of Science, Stanley pursues them on their way to South America in order to retrieve his longtime friend and leader.
Stanley is a tall, well-built man with hyperbolically prettified facial features. He has arched eyebrows and relaxed-looking, light colored eyes with thick eyelashes and glossy, colored lips that resemble wearing lipstick. His hair is of medium length and neatly slicked back, with a large strand falling in his face and the small area around his ears shaved short. His petrification scar runs horizontally across his face in a jagged line. However, after being revived it seems to have healed to the point that the jagged line is not as visible, instead two jagged lines are seen along the bottom of his eyes.
When in battle, he wears a large suit of armor which covers most of his body along with his head. The armor is extremely intricate, with large shoulder pads that are decorated with a feathery material hanging from the bottom of them that covers Stanley's body like a cape. The mask he wears with this armor is surrounded with similar material that hangs off his head, somewhat resembling a lion's mane and incorporating gas mask filters.
Outside of battle however, he wears a dark bodysuit with gloves, a back holster, knee pads, and armored greaves that have spikes on the side of the soles. Even in this state, he also carries a large bolo knife in his belt and a pistol on his hip at all times. He is usually seen smoking a cigarette.
Years after the second petrification event Stanley is given a new uniform that is similar to his old one but with slight modifications. He now wears clawed gauntlets that extend past his elbows. He retains his scars most likely due to weathering on his statue.
From what is seen about Stanley, he appears to be a "shoot first, ask later"-type of person. This was seen when he attacked the Kingdom of Science when they arrived, despite them doing nothing to warrant an attack. However, Xeno stated that this was because Stanley wanted to elaborate to them the advanced skill of his benefactor, should they be hostile.
He does get amused when he finds something interesting, as seen when he was intrigued by the Kingdom of Science dodging his machine gun fire, bringing down his airplane, and Gen lying about the Petrification Device to allow his allies to escape him. Owing to his past as a soldier, Stanley is very observant of his opponents. He carefully inspected Senku's group as they hunted alligators to find out how much threat they pose to him and his allies. When he prepared to take Gen away, Stanley performed a pat down for weapons. Furthermore, Stanley sent Luna as a spy to draw out the science leader, knowing full well that they would help someone in need and that they wouldn’t abandon an ally.
Stanley will also get frustrated if he fails in a way, suggesting that he is a perfectionist. This was seen when he expressed anger at learning of Senku's survival or Senku's group escaping. Dr. Xeno makes a scorning remark about his frequent habit of smoking, something the former has no problems with. Stanley has no qualms about endangering and potentially killing the intruders, regarding his previous assault on them merely as a show of power. When Luna question him about on wanting to murder the alleged science leader of the opposing team, he silenced her with a mere cold-blooded glare. Once the former soldier locks Senku as his target and gets permission to shoot from Xeno, he unflinchingly attempts to assassinate the teenager without a single shred of doubt or hesitation, indicating that he will resort to cruelty without question if he gets the okay from Xeno. Nevertheless, he is still a professional soldier, and as such, respects the rules of war. Francois concludes that he will not attempt to harm Suika or them, provided their identities are truly that of civilians unrelated to the Kingdom of Science. Although he respects the military code, not only is he capable of murder, but also an indiscriminate, systematic elimination of anyone who opposes his military objective. When realizing that he was going to be petrified a second time, Stanley initially tried to prevent it but then gave up after realizing it will be in vain and not being willing to doom humanity. He showed himself composed in the face of defeat, as he complimented his enemies before he took one last smoke from a cigarette and was petrified again.
Attesting to his extreme willpower to endure four millennia under the effects of petrification, Xeno doesn't doubt in the slightest that Stanley can complete a task once he sets his mind onto it. Stanley himself even confirms this by stating no matter how hard the task is, he can get it done. While he does seem to show strong loyalty to Dr. Xeno and faith in his abilities, he doesn't seem to hold his other allies in high regard. Of note, once he shot Senku, rather than retrieve Luna, who was still enemies with the Kingdom of Science at the time, he chose to leave her there, despite her status as a spy becoming known and showed no concern for her safety or even an attempt to rescue her in.
Stanley will do anything to ensure Xeno's safety. His loyalty stretches beyond companionship, being ready to commit atrocities so his friend can establish a world according to his ambitions. Within moments of being petrified, Stanley decides to put his existence and freedom on the line so Xeno can continue pursuing his dream.
After his revival, he immediately asks to know what his next job will be and since Xeno is there to brief him, he seems to no longer be hostile towards the Kingdom of Science. It's implied that since Xeno's plans of world domination are no longer viable with so much of the population revived, neither of them will attempt anything similarly ambitious again since they understand the consequences. 
Abilities and Skills
Stanley is a capable warrior with years of combat experience. Xeno vouches for both his skill and tenacity, describing him as his capable knight. Charlotte and Max also compliment him as skilled, saying the Kingdom of Science would have no chance against him. Indeed, the Kingdom of Science had to start another Petrification event to defeat Stanley otherwise they would have suffered a major loss of their allies.
Combat proficiency: Judging from his background, as well as his assault on Senku's group, Snyder is a valuable member of Dr. Xeno's group for his skill in modern warfare. At first glance, he could tell that Gen was not a developed fighter and that Senku's warrior group should be approached with caution. He has good reflexes, as he casually avoided a spear strike from Moz with little effort.
- Skilled Strategist: He initially planned on wiping out the entirety of the ship crew with a decisive strike, only to lose his aircraft. Eventually, he took one of their members in for intel instead. To draw out the science leader, he sent Luna and told her to signal to him once she located him. Furthermore, Stanley was able to identify his target after deducing that he would look at Luna and then in his direction. By keeping himself hidden in the submarine and letting his unit attack, Stanley was able to successfully commandeer the Perseus after taking down both Moz and Matsukaze.
- Marksman: Stanley uses a variety of weapons, such as a machine gun. While Stanley is skilled, he was unable to hit members of the Kingdom of Science, but did graze Matsukaze in his shoulder. Stanley is also capable of judging the velocity and distance for a single sniper shot, by using the stripes on Luna's outfit. Even while his enemies were escape in the dust cloud Stanley was still able to successfully shoot both Tsukasa Shishio and Hyoga in the shoulder.
- Mental Resilience: Among the select few that are mentally strong enough to withstand the millennia-long effects of the Petrification, Stanley possesses an extreme amount of determination. Stanley believed from years of training as a sniper, that being petrified would be no problem for him. Immediately after Dr. Xeno suggests eliminating Taiju to bring down their adversaries, Stanley is set on the task. When inquired by Gen on how he can pull such a feat, he simply assures him that he is capable of it without justification.
- Gifted Intelligence: Aside from his military position and status, Stanley is also quite intelligent; amidst the ruckus on the ship caused by Luna accidentally giving out Stanley's position, the latter deduces that their chaos and amateurism works to his benefit - the moment "the sharp-minded" Senku looks in his direction, the soldier correctly identifies him as his designed target. While Stanley is not proficient in Science, Stanley is capable of understanding of that there was a Science user among the enemy. Adding to his perceptiveness and predictive ability, Stanley is successful in assuming Xeno will leave a "code" of sorts by moving his mouth, as if talking. This allows him to locate the next destination of Kingdom of Science's vessel and act accordingly.
Stanley carries a machine gun on him. He also carries a pistol and a dagger on his side.
- Stanley is the first named character in the series shown with a smoking habit.
- Inagaki originally intended Stanley to look more like Daisuke Jigen (a grumpy old man), however Boichi chose to make Stanley flashy and pretty instead.
- While in uniform in the flashbacks he's shown wearing a variation of the US Parachutist Badge.
- In his Knight File from volume 18, Stanley is described to have thrown a football from outside the stadium, however in the Japanese version he is said to have shot it instead.
- He is the fifth antagonist to be petrified in order to be defeated, following after Tsukasa, Hyoga, Moz, and Ibara.
|Male||Brody Dudley • Carlos Barrios • Leonard Maxwell • Max Adams • Stanley Snyder • Xeno Houston Wingfield|
|Female||Charlotte Bony • Luna Wright • Maya Biggs|