Characters with big teleportation hitboxes such as Hood Sickle and Night Shift can go through the gates and allow the players to access whatever is inside. This glitch also appears to work on a few other Traptanium Gates as well, besides Light and Dark.
Knight Mare is able to exploit the glitch in at least the Wii version of the game using her secondary attack, though it's not confirmed it'll work on every glitched gate.