Dagger is a large, bipedal great white shark with quill like fins on his head, back, and arms. He's about 4 feet tall (1.2 meters). His hands and feet are webbed, having 4 fingers (including his thumb, seperate from the webbing) and 3 toed, dinosaur like feet. He has a long, thick tail with a large tail fin, with a small, triangular indentation between the top and bottom half of this fin. His eyes are gray, but they can turn red or yellow, depending on his mood. 2 sharp teeth stick out the sides of his mouth. He's a blueish gray color, with a lighter tone on his belly, muzzle, underside of his tail, tips of his arm fins, and webbing. The fins on his arms are sharp, and used for attacking.
When in this form, he's 3'3 (1 m) tall. He has gray tinted, light blue fur, with messy quills. His eyes are still gray, shining yellow in the light. His hands and feet are normal, and he has small fangs. His tail is slightly longer than a normal hedgehog's tail, with a small lump near the middle of it. He has normal hedgehog quills on his back. He usually wears a white polo shirt when he's like this.
Dagger is somewhat unpredictable; he tends to have mood swings often. Sometimes he wants to be alone, and sometimes he'll do anything for attention. He usually hates being alone, wanting to be with at least 1 person. He's often kind and gentle, but if he smells blood, his eyes turn red, and he chases people until he catches them (and attempts to eat them), or gets tired. He usually gets tired before he catches anyone. He loves to eat meat and fish, and will even eat it raw. At night, he usually sits by water and stares at it, remembering his life before he was a Mobian. When he gets turned into a hedgehog, he is a bit less quiet, and acts a bit peppier. He seems to be interested in Amy Rose, but he isn't sure about the idea.
Dagger was originally a Mobini, in the ocean. Someone (Dexter) dumped a strange, mutating fluid into the ocean, killing most fish nearby. Dagger became mutated by the liquid, becoming a Mobian. He still had gills, but could breathe above water as well. He became curious of the Mobians at the beach nearby, and tried several times to befriend them; he failed most of the time, and the people ran away. He was sad because of this, and left the beach. He met Gyro and Simone at Simone's house when he was sleeping in a tree, making everyone panic about a "tree shark". He actually managed to befriend them, improving his mental attitude. He usually stayed in the swimming pool in her backyard, feeling comfortable in the water. Around Christmas, he started staying inside, getting cold often, and becoming sick. He met Amy while she was walking to one of Simone's parties, acting a bit strange. He followed her, and smelled her, liking her perfume. He followed her to the party, where Mikey turned him into a hedgehog. He started talking to Amy more, being somewhat shy and embarrassed. Eventually, they made friends, and he was content with his sucess.
Dagger has super strength, being able to lift things almost 100 times his size. His thick skin makes him able to shrug off a lot of damage, ignoring most minor threats.
In this form, he's super fast, able to keep up with Sonic (when he's going slower than usual). He also loses the feral "feeding frenzy" urge in this form, making him less aggressive.
Dagger can swim extremely fast, being able to swim alongside a fast motorboat at a decent rate. He can tear through metal with his teeth, but doesn't do that often. He can breathe both below and above water, making him able to survive in most places. His sense of smell is very strong, being able to smell blood almost half a mile away.
He can run on top of water in this form, and has excelent hearing. He can pinpoint where a noise is coming from, even if it's very far away.
He's very slow on land in this form, not being able to catch or evade much. He depends on his thick skin for defense, and if he can't catch someone, it's just too bad. He's also very gullible.
In this form, he loses almost all his ability to swim. He will jump in the water blindly, and almost drown as a result. He thinks a bit too much as well, stalling over a trivial piece of information.