Kassey and his twin brother Patrick are pyrotechnicians who make fireworks in the valley. Kassey is the best pyrotechnician in the world and his brother is the second best. He is serious about his work, and is proud of the work he creates. He may be a bit harder to get along with than his brother, but he's not a bad guy. Kassey has a smiley face on his overalls, which is how you can tell him apart from Patrick.
Unlike his brother, he seems desperate for companionship. He can be seen harassing Muffy to go on a date with him in an event, and if you are playing the female version, he will constantly ask the player to go on a date with him.
Fireworks by the twins get displayed at the fireworks festival every summer. If you don't have a girl with a green heart level or higher, you'll watch the display with the brothers.