The hologram was part of Doc Greene's float during the Lobster and Technology Festival. Flobsters on Parade The hologram was active when Doc Greene, Cody and Frankie paid a visit to the Hall to retrieve the weather machine from the "Best Left Forgotten" room.
Doc Greene, Cody and Frankie momentarily mistook the Chester A. Arthur hologram for a ghost and used the Doc's Spectral Vapor Filter on it. When the device had a similar effect to the one it had on the so-called ghosts infesting the town, the trio realized the "ghosts" might be holograms too.
Finding themselves in an alternate timeline in which Doctor Morocco ruled "Moropolis", Cody and Frankie visited the Hall and activated a rather irritable version of President Arthur. They managed to get him to fill them in on how Morocco had changed history so they could later go back and fix it.