Esai Morales of "NYPD Blue" and Amy Madigan of "Grey's Anatomy" are making special appearances on the upcoming season of "How to Get Away with Murder."

At the Television Critics Association summer press tour, showrunner Pete Nowalk confirmed that both actors will have guesting gigs in the new series. However, he refused to provide details on their episode counts and character descriptions.

The new series is also set to bring back Madigan into the Shondaland fold, following her recurring stint as the psychiatrist of Meredith Grey. She also made appearances on "Criminal Minds," "From Dusk Till Dawn: The Series," and "Mozart in the Jungle."

"Dexter" alum Luna Velez will also join the cast of season 3 as the president of the university where Annalise Keating works as a professor.

In an interview at the ABC's summer Television Critics Association party, Viola Davis, who plays Annalise Keating, revealed that the first episode of season 3 will feature a big reveal.

"A mystery is going to be revealed in the first episode that is so big and so unbelievable I just think it's going to cost everyone something," she said.

The actress also shared how every season of the series leaves her in shock.

"Every time I pick up a script, especially the first script of the season, I'm always shocked," said the Davis. She added that the mystery in season 3 is going to be too big for them to figure out.

"We have been sitting on set, all of us, in different groups, and just talking about the mystery that's going to be revealed. We cannot figure it out! Last year we could figure it out, especially Alfie Enoch. They are just highly intelligent kids. But this year, cannot figure it out!" she said.

"How to Get Away with Murder" season 3 premieres on September 22 on ABC.