Paul Dini couldn't be happier for Harley Quinn.

Not only is she is celebrating her 25th anniversary with an all-star comic book special, she's also taking over Batman Day on Sept. 23 from Gotham City's resident do-gooder -- a move that doesn't surprise him, at all. If DC Comics hadn't made the change official, Dini jokes, Harley would have done it herself.

RELATED: Harley Quinn Invades Classic DC Covers for Batman Day

Dini co-created the fan favorite character in 1992 alongside visionary DC Animated Universe architect Bruce Timm for Batman: The Animated Series and Harley Quinn has become one of the most beloved characters in all of comics. After headlining the live action Suicide Squad film last year, the breakout character is now being feted with the Harley Quinn 25th Anniversary Special, a 48-page comic book featuring stories by Amanda Conner, Jimmy Palmiotti, Chip Zdarsky and Joe Quinones.

Dini also has a story in the special titled, "Birthday Blues," with art by Chad Hardin. The award-winning writer and producer reveals details about the story to CBR, and also shares his thoughts on Harley's legacy, as well as his own plans for Batman Day. And, in possibly the most exciting news of the interview, teases two more potential projects starring the Maid of Mischief.

CBR: Harley Quinn turns 25 this year. Did you know you had created something so special – and beloved – when you introduced her along with Bruce Timm back in 1992 on Batman: The Animated Series?

Paul Dini: I knew that I liked the character a lot, and I hoped that a little bit of that would shine through once she was animated. You never really have any idea how a character is going to turn out when you're writing the thing. You just hope for the best. But when you have a good team working on the animation, that's when the character really pops. I remember when I saw the episode of "Joker's Favor" completely animated, I thought Harley turned out really nicely. And she came out funny and appealing and quickly became a character that we all wanted to see again so we kept in the backs of our minds that we would do another episode where she would feature in as the Joker's helper and then after we did another couple of them, we realized that we had a character that the crew liked an awful lot and thought that she adds a lot to the Joker, so let's keep her around.

I want to speak with you about Batman Day but first -- did you know that Harley's anniversary is actually mentioned as a "Moment" on Twitter today, alongside memorials for 9/11 and updates on Hurricane Irma and the new iPhone? That must be somewhat surreal.

She's a moment? I didn't notice that. [Laughs] But that's really nice. I know a lot of people like her. I posted one panel on Twitter from my story in Harley Quinn 25th Anniversary Special that comes out on Wednesday and I just now saw that I have 39 notifications of people who either have something to say about that or Harley or various other Harley things so that's cool. It's nice knowing that she's out there in the public consciousness. I think it's great when I see somebody dressing up as Harley. And it puts a smile on my face when I walk into the candy store and there is a Pez dispenser with her face on it. That's pretty neat.

In the Harley Quinn 25th Anniversary Special, your story is titled, "Birthday Blues" and it opens with a series of unfortunate birthday parties that are not easily forgotten by Harley. What was your worst-ever birthday?

[Laughs] I agreed to appear at a convention. I believe it was the Chicago convention over my birthday, which is August 7. And this was about maybe 17 or 18 years ago. I did the convention and it was fine, but on the actual day of my birthday, everybody else was busy with convention stuff and I was sitting in my hotel room alone because I had done all of my panels and signings and every thing else. I just ate room service. Everyone else who said they could do breakfast or something fun all cancelled, so I flew home from Chicago by myself thinking that was a pretty punk-ass birthday. Since that time, I have been really down on doing a lot of conventions. I was doing a lot more of them at that time, but after that it felt like the lonely comedian's birthday on the road when you go out and do your jokes and then sit in your hotel room. After that, I said, "No more."

I don't want to spoil too much, but in your story, we learn that the Joker may not be as genuine as he presents himself – no real surprise there. But for once, couldn't he have been sincere with his birthday surprise?

No. [Laughs] I think if the Joker had not had a conflicting robbery that night, he would have gone through with planning her birthday party, but once he had the robbery, he thought business before pleasure. But he is reminded of what his priorities are by Poison Ivy. I think Harley and Joker do have some nicer moments. The stories that I have been doing with Jimmy Palmiotti in Harley Quinn are probably about as fun and affectionate as he can get but he is the Joker after all.

You mentioned that it's Poison Ivy that saves day and Harley's party. She's always enjoyed a special connection with Harley and soon the dynamic duo is heading to Riverdale to face off against Betty and Veronica for Archie's affections. What can you reveal about this epic crossover?

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It happens that Harley and Ivy venture to Riverdale when Ivy learns that something that Mr. Lodge is doing is potentially upsetting to her personally and to the ecosystem. Even though Lodge is claiming that it is something very benevolent. Ivy decides to take it into her own hands to stop it and Harley comes along to help and support her but she ends up running off half-cocked and having a good time as she always does. That brings them directly into conflict with the Archie Gang: Betty, Veronica, Archie, Jughead and the rest of them. In this one, Ivy actually has some altruistic motives, but you can see why what she is doing is important but she goes about it the wrong way, which leads to trouble for both groups.

Harley is 'officially' taking over DC Comics' annual Batman Day on Sept. 23. What are your thoughts on this not-so-hostile takeover and what are your plans for Batman Day?

Yeah. That sounds like something she would do. [Laughs] You can't stop her once she gets something into her head. The fact that Batman has a whole to himself and it's her anniversary, she must have felt that she had to do something about that. He gets Batman Day every year. I will just take this one for myself.

My plans are that I am going to be at the Barnes & Noble in the Grove here in Los Angeles talking about Batman and of course, Harley, and just about whatever people want to talk about be it the history of Harley, or the history of Batman, or about my graphic novel, Dark Night: A True Batman Story, which came out last year and just came out in paperback and any future plans that I have for the characters. It's going to be a big Batman and Harley party.

What are your future plans with Batman or Harley? Do you even have any?

I do, but some of them I have to keep secret for right now. [Laughs] I can say that I will be revisiting Joker and Harley's relationship with Jimmy Palmiotti in the not-to-distant future. I really enjoyed writing those back-up features for Harley Quinn, but Harley is taking some time off this fall to run for the Mayor of New York, which will be a lot of fun. But I think we will be looking to tell those stories in a spinoff book. Jimmy and I have to plot out exactly what that looks like and when that's going to happen. We do have tons of ideas but we'll be returning to Harley before you know it.

And I have some stuff of my own that I am kind of keeping a lid on until around Halloween, and then I will have a bit more of an announcement.

Harley Quinn 25 Anniversary Special is available now from DC Comics.