Captain Spearhook is the captain of the "Spearhook Swashbucklers" and the former captain of the royal guard before Undyne. Although he is not related to Undyne, her father was a member of spearhook's crew taking the position of first mate. Spearhook was also had fought in the human monster war alongside with King Asgore, Semi (the grandfather of the Sans and Papyrus) and Gerson.
He is a humanoid fish with blue scaly skin and messy red hair and a small pointy red bread. He has a very bulky physique and has a large gut. He wears a old white shirt with a red pirate robe, a black belt, large worn out brown boots, big dark red trousers and a black pirate hat with a symbol that resembles a fish monster head with crossed spears. He has a blue spear attached to his right arm, it's what got the Captain his name.
He usually acts like a pirate captain, even screaming AAAAAARGH like a pirate. Much like Undyne, he is loud, over the top and outrageous, cares deeply for others (mostly his crew) and enjoys entertainment. Due to the war and the "Chara Incident" he has a deep hatred towards humans and will do literally anything to get a Human soul.
Undyne's Dad was the first mate in Spearhook's crew after he saved Spearhook from drowning. Since then they have been the bestest of friends.
Spearhook was a father figure/mentor to Undyne who even helped her in training to be a royal guard. He also the reason why Undyne hated humans at first.
He was a elite royal guard who had served under Asgore for a long. Much like Undyne, he had to defeat Asgore himself in order to be a knighted as the Captain of the Royal Guard.
Semi the Skeleton
Semi was another fellow guardsmen who worked alongside Spearhook. Spearhook really enjoyed his jokes and even training with him.
Gerson was the general of the Royal Guard and Spearhook's superior. Spearhook at first didn't like gerson that much, saying that he was a "Slow and weak little turtle" and usually made fun of him behind his back. However later during the war they slowing became great allies. Even after the war when they got trapped in Mount Ebott, they still retained their friendship and Spearhook oscianally visits Gerson's shop to buy Sea tea and Crab apples and to share some stories.
Chara and Asriel
Spearhook was overjoyed the day when prince asriel was born and had always looked into the young monster prince's good interests. He always was a bit over protective of Asriel and at times accidently beaten up any monster that tried to get near the prince. But then came the day that chara would fall to the underground and would meet Dreemurrs. Spearhook wasn't a big fan of them from the moment he met them. he even to to take their soul, but were stopped by the King and Queen, who would later adopt the fallen child. After a while he started to like Chara and at times would even bring gifts for them. However, things wouldn't be the same after the tragic incident that would follow. After they perished, Spearhook felt bad for not only himself or the Dreemurrs but also for all the other monsters who loved the human child, thinking that hey would bring a new era of peace between both Humankind and Monsterkind alike. Soon, he found out that Asriel had absorbed their soul and had headed up to the surface to the human home village, only to be attacked by the humans up their. This lend to Asriel demise, breaking the hopes and dreams of the entire underground. Disheartened and outraged, Spearhook blamed the human for Asriel death, leading him and the rest of his companions to grow a strong hatred towards all humans.
- Captain Spearhook is somewhat similar looking to Masa form the Undertale AU Inverted Fate.