Warning: The following contains SPOILERS for Doctor Who season 12, episode 1, “Spyfall - Part 1.”

The premiere episode of Doctor Who season 12, “Spyfall”, boasts an outstanding collection of cameo appearances, in addition to the return of the core cast from the previous season. This resulted in an impressive ensemble made up of comedy legends, dramatic mainstays, and promising newcomers.

The action of “Spyfall - Part 1” saw The Doctor and her companions being gathered from around Sheffield and transported to London at the request of MI6. Spies from every covert organization in the world had been attacked by alien beings and MI6 had taken charge of the investigation, due to the recent closure of UNIT and Torchwood. This leaves The Doctor and company in unfamiliar territory, working with new allies against a menace that The Doctor has never encountered before and cannot identify.

The one lead regarding the aliens was that every agent who was attacked had been involved in investigating a tech-magnate whose search engine and social media software give him access to unprecedented amounts of data. This leads the Doctor to seek out O - a former MI6 agent with an amazing insight into the actions of aliens on Earth and perhaps the only person who knows anything about the threat they are facing. Here’s a rundown of every core character returning for season 12 of Doctor Who, as well as the actors playing them and the supporting cast for the premiere episode.

The Doctor & TARDIS Crew

Jodie Whittaker as The Doctor: Previously best known for playing Beth Latimer in police drama Broadchurch, Jodie Whittaker is also the first female actor to play The Doctor. Not much seems to have changed for The Doctor since season 11, though she has apparently adopted an abandoned garage in Sheffield as a base of operations so she can be close to her new adopted family when they aren’t traveling the whole of time and space.

Bradley Walsh is Graham O’Brien: Bradley Walsh was best known as Ronnie Brooks in Law and Order: UK and as the host of game show The Chase before being cast as Graham O’Brien in season 11 of Doctor Who. He returns as the retired bus driver for season 12, having found a new zest for life traveling with The Doctor after the death of his wife and having developed a warm relationship with his step-grandson, Ryan Sinclair.

Tosin Cole as Ryan Sinclair: Tosin Cole played regular roles in The Cut, Eastenders and Hollyoaks before being cast in Doctor Who. He returns as Ryan Sinclair; an aspiring electrical engineer, who suffers from dyspraxia. The new season finds Ryan more confident in his physicality, playing basketball with his friends on a regular basis when he isn’t traveling with The Doctor.

Mandip Gill as Yasmin “Yaz” Khan: Before being cast in Doctor Who, Mandip Gill appeared in the television series Love, Lies and Records, Doctors and Hollyoaks. She returns as CP Yasmin Khan; a probationary police officer and old schoolmate of Ryan’s. The new season finds “Yaz” caught between a rock and a hard place, as she finds herself lying to her family and her supervisor in order to spend more time traveling with The Doctor.

Sacha Dhawan as O/The Master

Sacha Dhawan is perhaps best known for playing Steel Serpent in Marvel’s Iron Fist. While this is his first appearance on Doctor Who, he played director Waris Hussein (the director of the Doctor Who pilot episode in 1963) in An Adventure In Time And Space. He appears here as O - a recently dismissed MI6 “horizon watcher,” formerly tasked with keeping an eye on potential alien activity. A pen-pal of The Doctor, he is the only person on Earth who seems to have any idea on how to counter the current crisis, but is later revealed in a shock twist to be the new version of The Master, the Doctor’s “best enemy”.

Spyfall’s Supporting Cast

Stephen Fry as C: First finding fame as half of the comedy team of Fry and Laurie, Stephen Fry is today regarded as one of England’s finest wits as well as a great writer, actor, comedian and political commentator. He is perhaps best known internationally for playing Dr. Gordon Wyatt on Bones and the Master of Laketown in The Hobbit movies. He appears here as C; the leader of MI6, who is responsible for calling The Doctor into action after every intelligence agency in the world reports their agents are being attacked by strange alien beings that can walk through walls.

Lenny Henry as Daniel Barton: A legendary comedian and actor, Lenny Henry has starred in several comedy shows baring his name and co-founded the charity Comic Relief. More recently, he played a dramatic role as Ed Burnett in the third series of Broadchurch. He appears here as Daniel Barton; a tech magnate whose company is said to be more powerful than most nations. The Doctor and company begin looking into Barton’s company, after learning that all of the spies who were mysteriously attacked were investigating him.

More: Doctor Who: What Happened To Jenny, The Doctor’s Daughter?