According to what little bits of the issue that have been made in the story so far, it is implied that the Tweedles had, once again, been having a paintball battle. It had culminated in the twins taking out a paintball cannon of unknown origins that hit Charlie right as he was at the Windsor staircase. He had apparently fallen down, hit a squeaky mallet, fell some more, before finally crashing into the potted plant next to banister end.
He had since then been in traction for many weeks and the post of Acting Prefect had then been given to Blaine. Charlie wasn't present when Kurt was officially brought into Windsor House and had missed (and had been uninformed of) all the ongoings in the succeeding episodes before he returns, still a little banged up, in the episode Paint.
Charlie appears to have excellent command of the Windsor boys who obey him strictly when he tries to rein in the pandemonium. However, he too does subscribe to the Windsor type of attitude as is proven when he allows the twins to retain the prized Pavarotti out of vengeance towards Logan and Stuart House. Charlie is described to be tall, and have unruly brown hair and cornflower blue eyes. He is also an athlete as his build (and implication of throwing javelins) attests to.