EXTRA AVOCADO! Sonderegger
The description on the BGG store reads (to me at least) as though these are new characters for the game, which doesn't make sense as they are already included in the game.
In fact, they are alternate versions of two characters from the base game. Here are the base game cards for Nathan and Victor:
They are new versions of the characters, and they play differently. Other than thematic reasons, there's nothing stopping you from playing both old and new in the same game.