Two add-ons are available--Feastday Prank Pack and Feastday Gifts--priced at $2 / 160 BioWare Points / 160 Microsoft Points each, with a Feastday Combo Pack bundling the two and offering some savings at $3 / 240 BioWare Points / 240 Microsoft Points.

Included in the Prank Pack are "ten unique feastday pranks that your party members will love to hate," such as the protective cone for dog, plus "two types of gifts to let you apologize afterward." The Gifts DLC includes "ten unique feastday gifts that your party members are sure to love," like Morrigan's functional Alistair voodoo doll, and "two types of lousy gifts to let your companions know you weren't completely serious."

You may think this a clever prank from developer BioWare, but a quick look at the Xbox Live Marketplace reveals it to be legit. In fact, I bought some, just to make sure :|