The four main ghosts in the regeneration chamber
The Regeneration Chamber, also known as the Ghost House, the Unliving Room, the Ghost Room, or the Spectral Callback Zone, is a location that Ghosts can enter to have their flesh regenerated after they get chomped.
History
In Pac-Man, the Regeneration Chamber is in the center of the maze. Whenever the ghosts' positions are reset (i.e. whenever Pac-Man loses a life or completes a level), Pinky and Inky and Clyde appear inside of the Chamber and Blinky appears just outside its entrance. When a Vulnerable Ghost gets chomped, its eyes will return to the Chamber and its flesh will come anew as its normal color after a waiting period, marking the first appearance of the Regeneration Chamber's regeneration abilities. Pac-Man cannot enter the Regeneration Chamber.
In Pac-Man 2600, the ghosts are no longer distinct from one another, so no ghost starts outside the Chamber. The time the Ghosts stay in there is highly reduced.
In Pac & Pal (and Super Pac-Man too), the chamber is increased in size and Pac-Man has the ability to enter it. The Power Pellets in Pac & Pal were replaced with Galaxian Flowers, making this one of the only games where this chamber appears but does not exhibit its main function; however, it still fills a purpose, that being a place where Miru can stash the fruits she nabs.
In Pac-Man Arrangement, Kinky appears out of thin air with no eye input inside the box.