Ben McKenzie, Cameron Monaghan Ben McKenzie, Cameron Monaghan

No joke: Batman's most famous supervillain is coming to Fox's Gotham.

Although series creator Bruno Heller initially balked at introducing the Joker on the show's first season, he recently told TVGuide.com that the show would "scratch the surface of that story" after all. And indeed, the promo for Monday's episode (8/7c, Fox) features Shameless star Cameron Monaghan grinning a familiar grin and laughing a maniacal laugh.

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But is Monaghan's character the Joker? "I won't tell you that's the Joker, but I will tell you this is not a trick," Heller tells TVGuide.com. "This is not a game. This is the beginning of the Joker saga."But that's not the episode's only beginning. In fact, Monday's episode also introduces the Flying Graysons, the trapeze artist family of Dick "Robin" Grayson. How do those characters play into the Joker's introduction? And how does Monaghan's character cross paths with Detective Gordon (Ben McKenzie)?

Below, Heller further explains his change of heart about the Joker, how faithful Gotham will be to the Joker's origin story and whether he's worried that his stable of villains is getting a little overstuffed.

That promo suggests we'll be meeting the Joker this week. Can you confirm that?
Bruno Heller: We're not playing with the audience. I won't tell you that's the Joker, but I will tell you this is not a trick. This is not a game. This is the beginning of the Joker saga. We're telling the first chapter in the story of how the Joker came to be — where he came from, who he is, what started him on that path. We're telling a long and exciting story here, and this is just the first page of the first chapter. But this is not a red herring. This character is going to pay off big time.

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Cameron Monaghan's character is named Jerome. Who is he and how do we meet him?Heller: A murder happens at the circus and Jerome is a grieving victim of the murder. He's a young man who's deeply affected by the murder, which is why and how he comes into contact with Gordon. He comes from a tortured and dysfunctional family with many secrets that are revealed in this episode. It gives some insight into the kind of person that the Joker eventually becomes. He's a brilliant young man. He's a tortured young man. He's a man with many secrets, and many secrets are being withheld from him. He will discover things about himself and his past in this episode that lead him down a very dark path.

As you said, the path to the Joker is a long one, since we're still many years before Batman appears. Yet, the promo evokes the look and sound of the Joker we all know. How do you balance what he is now with what he becomes?
Heller:
We play with that a lot. I think when you see the whole performance that Cameron gives, the fullness of the character Jerome, you will see that. Obviously for a teaser for the episode, you want to hit the nail on the head because that's the business we're in. But you will see that he is both a familiar character and a strange character, and a character who has many other sides to him other than that particular couple of seconds you see there.

Next week's episode is called "The Red Hood," which comic book fans know has played a part in the Joker's origin story. How faithful are you being to the source material in this take
Heller:
We're being faithful and reinventing. Everyone has a different notion of what the source material is. It's a mythology with many stories and many facets that all can't possibly be true. To that degree, you have some freedom to invent, but you have other things that you have to be very faithful to. So, we tried to walk the line between invention and faithfulness. We always try to pay respect and honor to the best of the mythology, and we will never veer so far away from those kind of canonical moments that people feel we are telling some other story. It's very much about the Gotham that people know and love. It's like finding things out about your parents. There are always secrets to be discovered and always stories that you thought were true that turn out not to be true, and that's very much the spirit in which we're telling this story.

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This episode also introduces the Flying Graysons. How are they connected?
Heller: [Jerome] works at the same circus with Robin, the Boy Wonder's parents. The episode is also telling the story of the egg that hatched into Robin.People who are familiar with the mythology will know exactly where we're going with that story, and hopefully it is also a funny and engaging story in its own right.

How did you decided to feature the birth of a future supervillain and a hero in the same episode?
Heller: The show depends on both denying people stuff and giving it to them in full force. This is a graphic novel world, and sometimes too much is just right. It's an excessive world; it's a spectacular, larger-than-life world. So, this is one of those episodes [in] which we very much wanted to make a big splash. Sometimes you want to give people a huge bite, a huge chunk of the story just for fun. It's like turning up the volume to 11, so to speak.

Before the show began, you seemed adamant about not telling the Joker story for a while. What changed your mind? Did the addition of episodes or the early Season 2 renewal change your plans?
Heller:
Knowing that we have a second season to construct and looking in the long term was very much a part of this. But also, as the season unfolds, you get feedback from the audience, and we gather a sense of how the performance is playing out. It just seemed like the right moment. This is the beginning of a story line that we thought about for a long time, and we could have held back for longer. But you don't want to leave anyone in the audience feeling like you haven't given them your best shot. So, we listened to the audience, we got a sense of what they want, and this just seemed like the perfect moment.

Are you concerned at all about overcrowding?
Heller:
Oh, sure. That's the tricky game we're playing. As much as the audience demands more and more, sometimes we've given them too much. I wouldn't deny that. But I would rather give people too much than too little.

Are you excited to start the Joker story line?

Gotham airs Mondays at 8/7c on Fox. Watch an exclusive sneak peek from Monday's episode below.