The big-screen revival of the Teenage Mutant Ninja Turtles has done well enough to warrant a sequel. And so TMNT 2 (or whatever the title will be) is already greenlit for a 2016 release. The first film didn’t feature many fan-favorite elements from various previous Turtle incarnations, and it changed some of the stuff that was included. So what can we expect in the sequel? Director Jonathan Liebesman and producers Brad Fuller and Andrew Form have been talking, and they suggest there’s a chance that the TMNT sequel characters could include some or all of the following: Krang, Casey Jones, and Bebop and Rocksteady.

Read quotes on all that below, and see some concept art for Turtle designs that didn’t make the cut for this first film.

Let’s start with sequel stuff.

Screenrant asked Liebesman, Form and Fuller about going “big and sci-fi.” The answer was an excited “yes!” After posing the question, Liebesman queried, “Dimension X?” then said “F*ck yes.” But Fuller was more cautious, saying “I think what we need to do is we need to see how the movie does.”

That said, Fuller mentioned “we’ve talked about those worlds already.” And this little exchange followed:

Andrew Form: There are scripts that have been written for this movie that integrated those worlds into it already… Jonathan Liebesman: They were just too…it made the movie a bit too unfocused for this particular story.

Quick backstory about Dimension X. In various TMNT stories, that’s the origin of the TCRI ooze that transforms the turtles and Splinter into humanoids. It’s also the home of the alien villain Krang, and leads to some weird stories featuring other aliens, such as the Triceratons.

In the same interview with Screenrant, the creators said,

Form: We’re just finishing the movie but we all wish that we could put everything into the movie. We all have other characters that we wish we could have had in this movie. Liebesman: Casey Jones. Form: Casey Jones. Bebop and Rocksteady. We had those conversations throughout development of this movie but we’re launching this movie now in two weeks. Hopefully everybody feels the same way we do [about it]. We love them [Bebop and Rocksteady].

Digest all that while you think about this. Not only did some of the Dimension X elements factor into early scripts for the film that was released earlier this month, there were elements of the film that were changed considerably during reshoots. Da7e at Latino Review says,

…when I was on set, I saw TCRI ooze being fed into a bunch of Ninja-looking Foot Clan thugs (NINJA looking, not Mercenary Masked). Also William Fichtner was The Shredder. He wasn’t working WITH Shredder, he WAS Shredder. … Basically, even when I asked what was being re-shot during TMNT 2014’s re-shoot period, I was just told that it was stuff Megan Fox couldn’t do earlier because of her pregnancy. However, I watched them shoot a scene from multiple angles where April fought some ninja with a sai and Will Arnett’s Vernon did some brawling too. With ninjas on gurneys all around.

For more on changes that were made during production, let’s go to CBM, which has an interview with concept artist Kelton Cram. Cram says,

Shredder had a lot of changes throughout the process. The script would have big rewrites, and we completely revisited Shredders look and function. I got to spend a lot of time making numerous versions for Shredder.

Cram has a lot more to say about the design process for the film, adding,

Jonathan Liebesman had a lot of the ideas in his head about the different personalities of each Turtle, and how that would determine the size, costume, and accessories. It was all based on the original TMNT, but with a more cinematic approach. Donnie, the brain with the gadgets, Mikey the surfer, Leo the traditional one, and of course Raph the rebel. … They wanted all the Turtles to be unique in shape and size. Tall and skinny to short and stalky to even more brutish.

Obviously that’s not quite how things worked out, as we know from the final designs. But here are some images provided by Cram:

Teenage Mutant Ninja Turtles 2 will be released on June 3, 2016. Michael Bay, Brad Fuller, and Andrew Form will produce, while Josh Appelbaum and André Nemec will return as writers.