The solution to the mystery is that Bunnicula is not a vampire rabbit, but rather a "vegetarian vampire." He has a special digestive system that allows him to eat vegetables and turn them white as he absorbs their nutrients. He's not actually draining the life out of them, but rather consuming them very efficiently.
Here's how the mystery is solved:
* Harold, the dog, and Chester, the cat, initially suspect Bunnicula of being a vampire. They observe his strange behavior, his aversion to sunlight, and his ability to turn vegetables white.
* They decide to investigate Bunnicula's behavior by placing a carrot in a dark room with him. They check the carrot frequently and notice that it is gradually turning white, confirming their suspicions.
* However, they later discover a scientific article about "vegetarian vampires" that explains Bunnicula's unique digestive system. This article reveals that Bunnicula is not a vampire in the traditional sense, but rather a rabbit with a specialized digestive system that enables him to consume vegetables very efficiently.
* Harold and Chester learn to accept Bunnicula for who he is. They realize that he is not a threat and that his unique abilities are simply a part of his nature.
The mystery of Bunnicula is solved through a combination of observation, research, and acceptance. It teaches a valuable lesson about judging others based on appearances and encourages understanding and tolerance.