Grimm enlists Anne Dudek (Covert Affairs) and Keith David (Enlisted) to guest star on the show's current third season, THR reports.
Dudek will play Prof. Vera Gates, described as a smart and young archaeology professor.
She'll appear on the Grimm's "Once We Were Gods" episode.
Meanwhile, David will play Hedig, a ringmaster for a unique traveling carnival.
He'll appear on the procedural's "The Show Must Go On" episode.
Both episodes will air in the spring.