We return to our very occasional series “What’s That Thing on Top?” to update the status of one of the most notable things to be put on top of any Williamsburg building: the growth added to the building on Karl Fischer Row that is now known as the Ikon. We last viewed it from behind, when it was still a steel box. While we’re certain that the buyers of those units will enjoy their view of McCarren Park and Manhattan in the distance, we’re not clear how many residents are enjoying their view of The Thing. What we do know is that is quite the imposing presence from street level.