Yes, you can play a cut-down version of NiGHTS into Dreams on your Game Boy Advance by hooking it up to Phantasy Star Online on your Gamecube, but soon you'll be able to get a real taste of Nightopia in Sonic Team's online RPG with a special themed DLC quest just in time for Christmas.
Japanese players will be able to enjoy the 'Messenger From A Dream Quest' mission from December 13. Hopefully it will also make its way to Western versions of the game too, because it sounds lovely - a four-player quest that will feature the titular character throughout the stage.
According to IGN, players that complete the special quest will receive a key item which will allow them to unlock the 'NiGHTS Score Attack' micro-game we mentioned earlier. This can be downloaded to the Game Boy Advance via a Gamecube link cable.
Sonic Team also announced that it will be adding festive decorations to Pioneer 2 from December 19, with a Christmas tree and other holiday items dotted around the lobby. You'll be able to enjoy that until Christmas Day (December 25).