Final answer:
In The Lion King, Zazu is the character who rejects the idea of being a bigamist, emphasizing his moral and serious personality.
Step-by-step explanation:
The character who rejects the idea of being a bigamist and says, "Are you nuts? I'm not a bigamist..." is Zazu, from the movie The Lion King. This line is part of a humorous exchange highlighting Zazu's strict and moral personality, which contrasts the more laid-back attitude of other characters in the movie.