Bob Newhart. He picks up the phone.

It's a ninja. He kills everyone on stage, then leaves. After an interminable period of everyone lying onstage dead, they get up and go on with the play like nothing happened.

It is Godot. He punches out both of the main characters. They stagger to their feet and he punches them out again. Conspirators in the audience run onstage and pelt him with crucifixes and holy water. He screams and disappears through a trap door.

A goat. He poops out the remains of a printed version of that survey.

paulsc already won this thread, but:

It's Santa Claus. He staggers over towards the fireplace, as an empty PBR can falls from his coat and rolls over by the tree. Santa blinks a few times, then sticks his head in the fireplace and bellows: "LUCY! I'M HOME!"

Hearing no response, Santa picks up a fireplace poker and falls on the couch, cradling the poker in his arms and calling it "Rudy."

It's Tilk from long running hit TV show "Stargate SG-1". He informs the main character that they have no honor and they have bought shame on the people of the Tau'ri. He continues to stand left of stage with his arms folded. He says nothing more, but raises his eyebrows twice.

It's Filippo Tommaso Marinetti, who totally abolishes the techniques that are killing the passéist theatre.

Hitler. He does the ironing.

The stage manager. He scurries in a semi-crouch to an endtable on the set and turns off the ringer on the prop cell phone that has been ringing behind the lead actresses climactic monologue.

It's me, damnit! I play the bartender at Malone's who has to give the bad news to Sully about what happened with his sister.