Frankenflavours are combinations of two flavors which sell at a higher price than each individual flavor. Frankenflavours last for only 20 minutes before a regular flavor is sold again. The Heroic and Legendary levels require selling specific combos to unlock. These levels require the combo to be sold for a while, they do not automatically unlock upon the first sale of the combo.
Frankenflavours can be merged with addons to create frankencombos, these are like regular combos, but use frankenflavours instead of regular flavours.
Normal frankenflavour contains all the normal ice cream flavors. The level is automatically unlocked as the 4th quest reward at the beginning of the game. Previously, it was required to sell the "It's Alive!" combo before this would be unlocked.
Heroic frankenflavour contains all the heroic ice cream flavors. This level is unlocked by selling the "Frankenstein" combo.
Legendary frankenflavour contains all the legendary ice cream flavors. This level is unlocked by selling the "Dr. Whoves" combo.