[Boone is pretty much unaware of Egon's feelings towards him, since he hasn't really acted any different. Besides, he's not really good at picking up on that kind of thing. So when he sees Egon he gives him a small smile, present in hand, and only looks up when Egon mentions the mistletoe.

...Ah. His smile falters, a look of realisation crossing his face instead.]

Never done it myself, but... I know what it is.

[He meets Egon's gaze, and his ears twitch nervously. He doesn't know what to do here, it's not a situation he's been placed in before.]