Prof. Ratna Zhang is one of the pre-made NPC biology professors in La Fiesta Tech from The Sims 2: University. He can be made playable by befriending and asking him to move in, or by marrying him. Even though Ratna has black hair, his natural hair color is actually brown. He has the same facial structure as Ricky Mace.
Ratna's name is randomized when La Fiesta Tech is generated. The name "Prof. Ratna Zhang" is only referenced in the game files. He has 2 interest points in Sci-Fi which is relatively uncommon, given that almost all other NPCs, young adult and up have 4 points in Sci-Fi.