Sally Sundae is the twin sister of Shelly Sundae. The two of them were the owners of the "Sundae Sisters Ice Cream Parlor". One day, Shelly Sundae was experimenting a new flavour of ice cream but accidentally fell into the vat of ice cream.
When Sally explains what had happened to her sister, she described her as "different" after Shelly came out of the vat of ice cream. Shelly then left Sally and went missing. She secretly became the a super villain known as the Brainfreezer.
The Brainfreezer was then defeated and sent to prison and currently, Sally is the only remaining owner of the "Sundae Sisters Ice Cream Parlor".