This is the DVD box for "Sonic Christmas Blast".
After both SatAm Sonic & Adventures of Sonic (Weekday Sonic) were off the air, this strange "holiday special" was produced. It was animated in the style of AOSTH (wacky, with abstract backgrounds) & was clearly meant to take place in that universe. However, for some reason (That makes it famous) the producers (Seemingly at the last minute) added in Princess Sally from the SatAm Sonic series, though she only appeared in about 10 seconds of animation, and had no speaking part at all.
Seem strange?
It remains a mystery why they clearly shoe-horned in the character.

The episode itself is a little longer than a normal 'half hour' tv slot, and the plot is that Robotnick tries to take over Christmas, and make everyone else give him the gifts. (Both Santa Clause & Robotnick are fat guys in a flying thing...so it....makes sense?)