It's been 25 years since Tim Burton's Batman Returns hit theaters. Now, the director and the cast have revealed untold secrets about its production. The Hollywood Reporter recently sat down with Burton, Michael Keaton, Michelle Pfeiffer, Danny DeVito, and Christopher Walken to discuss the making of this sequel to the original 1989 classic, which was released on June 19th, 1992. Tim Burton was set on making weirder, darker, less kid-friendly characters, while Keaton cut out the majority of his Batman lines to let the suit do the talking. And then there is Danny DeVito, who improvised the Penguin's off-putting thick, black saliva with a strange concoction.

The sequel was supposed to usher in the merchandising aspect of Batman. More action figures, McDonalds tie-in, and generally much more merchandise, but Burton and his crew's twisted take on the return of The Dark Knight turned off many who were looking forward to cashing in on the Batman Returns money train. The movie was darker that it's predecessor at times and it was downright weird in places, which prompted McDonalds to pull out of the project. The main point of contention for the fast-food juggernaut? DeVito's black slime. Burton recalls that McDonald's was puzzled by "all of the black stuff coming out of the Penguin's mouth." DeVito went into detail about his custom saliva cocktail. He explains.

"The black saliva was a concoction that I came up with after working with the makeup and special effects people. Basically, it's kind of like mild mouthwash with food coloring in it. We had a jar of it with a nozzle on it. Before every scene, I'd squirt it into my mouth. Luckily the taste wasn't so bad."

Michelle Pfeiffer spoke at length about working in the latex Catwoman suit and working with a whip master. Apparently there were 40 cat suits tailor made for Pfeiffer's body because the latex was so thin, but the production only ended up using two of the suits after alterations were made. Michelle Pfeiffer said this.

"It was the most uncomfortable costume I've ever been in. They had to powder me down, help me inside, and then vacuum-pack the suit."

Michelle Pfeiffer went on to talk about a very important, but overlooked aspect of the suit. She explains.

"Originally they didn't leave me a way to use the restroom in the suit, so that had to be remedied as well."

Michael Keaton recalled that Batman Returns was first envisioned with a more talkative caped crusader, but Keaton ended up cutting out large pieces of dialogue to let the powerful suit utilize some non-verbal communication. As it turns out, there was another factor that led Michael Keaton to portray Batman with less words and pronounced movements. Keaton had this to say.

"It was a practical move early on to move in a certain way because they hadn't refined the suit and it wouldn't function properly. I got around that by making bigger, bolder, and stronger moves from the torso up, and it worked."

In addition, Michael Keaton says that he was not able to move his neck in the suit, making it nearly impossible to pull off a conversation for the Dark Knight.

Danny DeVito also spoke of the 4 and a half hour makeup process that he went through every day on set. He mentioned that towards the end of the project they had it down to about 3 hours. Since there were actual penguins on set, the area had to be kept cold to accommodate them, which worked out perfectly for DeVito since he had pounds of makeup on and a heavy coat. Christopher Walken recalls that the Penguins were treated very well on set. Walken explains.

"They had their own area on the studio lot with a swimming pool and refrigerated dressing rooms. They were very well taken care of."

Christopher Walken also went on to say that some of the penguins were nicer than others.

"There were three different kinds of penguins. There were the big ones, the Emperors. They were very docile and sweet. They would walk up to you and you could pet them like a cat. Then there was a middle size, who were a little more active. The smallest ones were very busy and aggressive, they'd give you a peck."

Another interesting fact is that long time Burton collaborator Danny Elfman almost didn't compose the score. He mentioned that the studio was urging for a more pop oriented soundtrack with contemporary hit makers, which alienated Elfman and he quit. He was asked to return soon after and went back to the set in London. Apparently what he saw inspired him because he started to write the score immediately on the flight home. Elfman said that he wrote most of the score in his head on the flight and would get up numerous times to hum into a recording device in the bathroom, prompting stewardesses to ask if he was ok.

While Batman Returns was a hit, it ended up making considerably less than the first movie at the box office, $145 million to be exact. Maybe that Taco Bell tie-in for the first movie helped out a little after all. Burton explains that he didn't feel welcome to come on board for a third movie and Michael Keaton admits that he just didn't like the script. The Burton/Keaton era was over after Batman Returns and both movies have stood up remarkably well nearly 30 years later.