Newt's better at beast language and social cues than wizarding so when he wants to express romantic interest or friendship to someone he automatically does so in magical beast inspired fashion. What methods does he use? How does he translate it into the human/wizarding equivalent? Will his friends and love interest figure out what he means? Does it involve strange gifts and even stranger activities?

Bonus ideas
* others having to use Newt's book or notes to realize what's going on.
* someone returning the gestures in kind either intentionally or unintentionally.
* including info on what beast the gesture is taken from and why it should be appropriate for the person it's aimed at. Maybe he keeps trying different species methods on the same person till he finds a match?
* talking about the ideas and/or the reactions to his gestures with the various beasts and complaining about the strangeness of humans/wizards