The Paragon Dance Party was created in an early issue. Its release to the live servers was supposedly an accident but was kept due to fan request. The zone was replaced by Pocket D and no longer has any zone connections. However, the zone still exists and is only accessible to developers and GMs.
This original dance party was run by DJ Zero, who did not appear in game until Pocket D was created sometime between the release of City of Villains (issue 6) and issue 7. Pocket D is a no fire zone where heroes and villains can meet and team up.
Though intended as a no-fire zone without enemy spawns, there was one instance when enemies appeared inside the zone. The day Issue 3 launched, Council and 5th Column troops battled in every zone in game, including spawning inside the Paragon Dance Party.
The old entrances to PDP still have the flyers outside their doors, however only a Bum nearby remains. PDP used to have connections in Talos Island at (403, 160, 5573), Independence Port at (-837, 0, 1222), and Steel Canyon at (-1680, 0, -2725) (though originally at (-4316, -100, 1778); it was moved due to being close to the Yellow Line, which made the PDP too useful as a travel shortcut).
The warehouse "skin" used to created PDP is also still in game. It is used in the third mission given to Natural origin heroes who start in Atlas Park, "Speak with Detective Brogan about the Skulls' attack".