Give me Newt, who is usually mild mannered, rambles on too long about his beasts and doesn't like making direct eye contact in a situation where he has to put someone in their place for making a move on his partner. Like, the partner in question is very clear that they're with Newt, but the other person cannot take no for an answer so Newt steps in to make a statement.

Bonus if Newt is a dick to whoever he's telling off and for his S/O being very appreciative of Newt's sudden display of possessiveness.

Double bonus if it's at an event with Theseus present who finds the entire situation hilarious because he's witnessed Newt's blatant assholery before.