Last month, it was announced that the theatre star and entertainer had signed up for the role of Danny Houston, who is the silent partner in Cheryl Brady's nightclub Chez Chez.
Speaking to Digital Spy about his new alter ego, Day revealed: "The producer has told me that he's the baddest on the block. There is going to be no-one badder than Danny Houston - he's about as bad as it gets and is the epitome of a soap villain really.
"I've been told that some soap magazines are nicknaming him Dirty Dan! For me, that's really exciting. He's a London villain and he's the silent partner in the nightclub. He's been involved in the business dealings from afar, down in London, and now he's going to come up and get involved on a personal level."
Asked how Danny will get along with Cheryl's brother Brendan, the actor replied: "Well, everyone's wary of Danny because of his reputation and what he's capable of doing. But it seems that the plan is going to be for them to be partners in crime.
"As Danny is 11 years older than Brendan, he's probably been there and done it all. He's probably given Brendan a lot of advice - what Brendan is doing now, Danny was doing ten years ago. From what I've been told, no-one will mess with Danny - and for an actor, that's really, really exciting."
Day makes his debut as Danny in tomorrow's episode of the Channel 4 soap. Viewers will then see him return to the programme in shocking circumstances later this year.
> Click here to read our interview with Darren Day
> Click here to read more from Darren Day in Soap Scoop