Accidental Pervert: Jonathan puts his hand through a female skeleton's rib cage, much to her indignation. Later, Dracula and Jonathan walk in on the same female skeleton in the shower and two fleas on their honeymoon.
Adorkable: He's an American surfer-dude backpacker klutz who tends to ramble about random anecdotes from his travels, geeks out over the monsters (once he's through being terrified of them), is quite considerate of the feelings of others, and is a hopeless romantic.
The Fool: He seems to be fine with taking a picture of a couple that's crying, adventuring through a "spooky forest", and following a trail of zombies on fire to an "awesome castle". He is also seemingly completely unafraid of Dracula though this is because he thinks the hotel is having a costume party when he first shows up.
Mayfly-December Romance: Mavis is just coming of age by vampire standards, but she's older than any living human and will long outlive Jonathan unless he becomes a vampire himself, which is never touched upon as a possibility.