Earlier today, the Smashing Pumpkins treated fans with a Christmas gift with a song called Have Faithe, Be Merrie. There are more details on the release of the song here.
Over the years, the Smashing Pumpkins have taken part in many festive celebrations. On December 12th 1993, they played Rudolph the Red-Nosed Reindeer at the KROQ Almost Acoustic Christmas Special. During a 2010 KROQ interview, Billy said that he felt that particular performance of Rudolph was poorly played.
At the end of a December 8th 2008 concert, the band opened a casket similar to the one featured in the Zeitgeist album booklet that contained many presents for the crowd. In true Pumpkins-style, Christmastime was played in the background. After the joyous occasion, Billy Corgan wished everyone a Merry Christmas and Happy New Year.