I assume you have talked to him?? If so, and he contintues the distracting business, I would call his attention to it, politely, during rehearsal.

It sounds to me like he's bored.  That he doesn't have the discipline to play his part as it should be played.  That he's looking for excitement, and (I think, possibly) approval in some sort of odd way by trying to make himself noticed.  That maybe he thinks acting is more improvisational, rather than slogging through memorized bits.

Two Things:

FIRST, I don't think you should bite your tongue to keep from laughing.  Go ahead and laugh.  Then let him know that what he has done was funny, but then explain to him how it was also inappropriate to the moment in the play and that it actually hurts the play as a whole when he does something to interrupt the flow or distract from the focus of the scene.  He has to understand that in a play everyone is working together to create a comprehensive whole. 

I like to use the orchestra analogy.  Everyone in the orchestra can be playing beautifully, but if the second clarinet is flat, or plays a passage in the wrong place, or at the wrong tempo, his actions destroy the effect of the entire piece.  The audience may even laugh at the clarinet, but afterwards, on their way home, they'll talk about how that clarinet player spoiled the whole concert.  The same kind of thing happens when an audience goes home from a play in which some particular actor has called inappropriate attention to himself.

SECOND, is there some place in the show where he can have his "moment"?  If he has a pretty bland part (second spear carrier from the left) is there a bit he can do (work on, come up with) that will allow him his little burst of spontaneity and still not adversely affect the balance of the show?  If you can give him something somewhere, maybe he will be able to restrain himself for the rest of the play. 

But you are going to have to make him understand that it's not about him alone; it's about the show and everyone in it.  That he doesn't have the right to single-handedly destroy what they are trying to create.  He may not really understand how it is that he's disrupting the show.  I would give him the benefit of the doubt and assume that he either came from an organization that prized improvisational behavior, or that he's incorrectly assuming that this is what "real" actors do.

In the end, if you dedicate a little time in helping him understand the importance of not being disruptive, it may be that that bit of attention will be all that he needs to turn himself around.  It's worth a try anyway. 

Best of luck.

 To politely disagree, I would NOT laugh at this young man. That is only going to reinforce the behavior.

Thanks for the comments. Maybe I should clarify. He is super awkward, even offstage. But as time goes on he is getting more and more awkward. I think he has no idea at all how he is coming across. But, I think maybe it is time for a private heart to heart. I think he has no idea at all how bad it is.

This is the downside of directing.

Originally posted by peacock Thanks for the comments. Maybe I should clarify. He is super awkward, even offstage. But as time goes on he is getting more and more awkward. I think he has no idea at all how he is coming across. But, I think maybe it is time for a private heart to heart. I think he has no idea at all how bad it is.This is the downside of directing.

In my experience in community theater from time to time you have to use "bad" actors for some roles, especially males. You just have to do your best to help him out and stop thinking of him as bad. He's just a beginner like we all were once. Go ahead and explain things to him in front of everyone, even if you have to tell him five times a night to keep still from now until opening. Having a "heart to heart"   might damage his confidence or inject emotion into the situation that doesn't need to be there.
Just my two cents.