Here's my answer to the burning question, "Just what do the infamous Ghostbusters wear under their uniforms when battling oozing, red slime??!!" (This Trivia follow up is from my April 16, 2022 posting.) 

When word reaches Doctors Stantz (Dan Aykroyd), Winston (Ernie Hudson) and Spengler (Harold Ramis) that slime has proliferated in the storm sewer of the big apple, the men waste no time in investigating. When one falls in to the goo, the others slip in themselves! All for one and one for all...

Exhausted and barely alive, the men are finally able to pull themselves out and get on their feet with their secret revealed in Columbia Picture's 1989 sequel, Ghostbusters II...

They wear Union Suits under their uniforms!

As luck would have it, they have landed outside of the Manhattan Museum of Art where Dr. Venkman (Bill Murray) is having dinner at a fund-raiser. They have to warn him! So, inside they go, no worry they are slimed and in their long underwear... 

But, how dare them barging in on such a hoity-toity affair in their Union Suits, messing up the place and shocking NY's high society! The police arrive to take them away!

They manage to get an audience with the mayor of New York and try to warn him of the impending crisis!

The mayor thinks they are out of their minds, it's late and, after much discussion, he dismisses them!

But wait, the GhostBusters are not to be deterred, their work is just beginning, plans must be made: 

Find GhostBusters II on DVD's or streaming for a look at this fun and entertaining film.