According to an interview with the game's planner and graphic designer Yukio Takahashi in the book 'Game Shokunin', it took him a whole year to finish off development of the game. He had to do everything but the programming himself, and drew all the graphics in about 5 to 6 months.
Contributed by ProtoSnake
Kissy's real name was revealed to be Masuyo Tobi when she appeared in Mr. Driller. Her name is a play on the Japanese phrase "Toby de arimasu yo" which means "I can fly".
Contributed by Mass Distraction