The songs, the deadpan humor, the fact that it was easy to get involved with the story even though the jokes emphasized how silly everything was (a nuclear reactor built by traveling carnies?).
What I didn't like
In the second half, things seemed to taper off ever so slightly. Not bad, just not as good as the beginning. Still, it all wrapped up nicely.
My overall impression
Think of how silly this title sounds and much it lowers your expectations; then invert that equation, and you get some idea of how laughably enjoyable BIGFOOT! THEMUSICAL is. Highly Recommended.