Princess Sally Alicia Acorn is a character created for the Sonic the Hedgehog video game franchise. Based off of the little squirrel who appeared as a supporting character in the early Sonic the Hedgehog games, she originated in the Saturday morning animated series spun off from the games (nicknamed Sonic SatAM by fans). She was the princess of the city of Mobotropolis, whose father had been exiled by Dr. Robotnik, and she was the leader of the Freedom Fighters, which Sonic the Hedgehog was a member of. This character, who was notably Sonic's love interest in the cartoon, would also appear in the Sonic the Hedgehog comic book published by Archie Comics, but made only one appearance in any of the games (cameos in the first and third bonus stages of Sonic Spinball).
Sally only briefly appears in the franchise's Christmas special, Sonic Christmas Blast, even though she had never appeared before in Adventures of Sonic the Hedgehog, the series that the special was spun off from. This makes the special Sally's only appearance in that particular continuity, though whether this version of Sally shares the same background details as her counterpart from Sonic SatAM is never mentioned. Early on in the special, she and Sonic "agree" that they will not get each other Christmas presents this year. Immediately following this, Sonic explains to Tails that he and Sally made this same agreement last year, but while he actually took the deal seriously, Sally actually did give him a bunch of presents, including a ring with a mysterious squiggle mark. This year, though, Sonic has figured out when Sally "say she wants no presents, she really means two stores full."
Sally is seen again at the end of the special, when Sonic, while distributing Santa Claus's gifts to everyone on Mobius, shows up to deliver her presents to her. Sonic then holds a sprig of mistletoe above her head and gives her a kiss.
It is worth noting that, except for an audible gasp, Sally never actually has any dialogue in Sonic Christmas Blast. A brief cut right after Sonic speaks with Sally at the beginning suggests that dialogue for her was already scripted and even animated, but was cut out because, for whatever reason, Kath Soucie (who had voiced the character on SatAM) did not agree or was unable to reprise the role.