“Hey, this is no time for chit-chat. Who knows how many more minutes the police can last against that...”
However...
“I can’t quite get the measure of you, boy,” the man said with a sudden grin. His mood had changed.
“The way you let yourself get caught up in talking about sweets while you work up a spell behind my back is pure mage. But there’s nothing mage-y about still going on about sweets way after you finished the spell.”
At that, Jack looked at Flat in surprise and Flat looked confused.
“Huh? Well, I got it ready because I thought you might be dangerous if you were an enemy, but since you’re not an enemy, activating it would just be a waste of magical energy and it wouldn’t be fair to you either, would it?”
“...”
After briefly observing him in silence, the man looked at Flat and continued cheerfully:
“Boy...what are you?”

Fate/Strange Fake: Volume 5, Chapter 14 ("Gold & Lions 1")