When you think of the personalities featured in the original Ghostbusters film, you probably think about five of its leading actors: Bill Murray, Dan Aykroyd, Ernie Hudson, Harold Ramis and Sigourney Weaver. But, according to the cast, there was actually another big star in the movie: the slime.

The original Ghostbusters cast opened up about their inanimate co-star back in 1989, when they appeared together on an episode of The Oprah Winfrey Show to promote the movies sequel. Oprah who, without hesitation, dipped her hand right into a bucket of the slime on stage asked the actors point-blank: What is this goo?

Its a food starch, I think, Ramis said.

A Chinese food starch, Murray added.

This particular purple slime was the films psycho-reactive ooze (mood slime) that lay beneath New York City. What most moviegoers didnt realize about the substance, however, was how often a new batch had to be created for filming.

Every few hours, they make it fresh, Murray revealed.

It wasnt always a simple undertaking, Ramis points out. There was a scene where I think 40,000 gallons of it were used in one shot, he said.

And it didnt seem particularly easy to remove from clothing, either. If you like that suit, dont get any on it, Aykroyd warned Oprah.

Now thats a high-maintenance co-star.

Another 80s film flashback:

Alan Ruck reveals the inside joke in Ferris Buellers Day Off