The standardized audience dialogue was largely developed at NYC's Wavery Theater, along with the complete list of audience participation props (water pistols, newspaper, rice, spinning ratchet noisemaker, confetti, rubber gloves, candles, toast, party hat, bell, playing cards, hotdogs & prunes). Veteran "audience cast members" know to bring extra and before the movie starts they patrol the audience asking anyone not "in costume," "Are you a virgin?" meaning is this the first time you've seen "Rocky Horror." If you answer yes, they'll give you one or two of their spare props so you can be part of the movie, too.
Some of the audience dialogue is even call-and-reply; half the audience sets up the joke and other half delivers the punchline. Like the squirt guns and newspaper. The audience only needs one or the other because half use the squirt guns to simulate rain happening on-screen while the other half use the newspaper to cover their heads (mirroring Susan Sarandon's actions).
If you've seen Rocky Horror without a properly rehearsed and correctly dressed audience, you only think you've seen Rocky Horror.
And you should never under any circumstances watch it for the first time without an experienced audience because it's not the movie that's entertaining, is the audience's collective ridicule of it that makes it worth watching.
There's even a sound track available online of the audience's "call backs" that can be synced to the video of the movie to get you closer to the live cinema experience.
https://rockyhorror.fandom.com/wiki/Audience_participation/Call_backs
(Adult language warning)
I agree. It was a hoot to go to those midnight showings
Only saw it in the theater once, as a teen back in the 80s. Went with a group of friends. We were likely a bit intoxicated.
We had no idea there was a rehearsed script of proper callbacks and my buddy kept shouting out random stuff at the wrong times, thinking he was playing along. We thought it was funny. The audience, I'm sure, less so.
Anyhow, few actresses ever looked sexier on screen than Susan Sarandon did, spending much of the film in nothing more than her underwear.
Be that as it may, Tim’s entrance scene is top notch. Only he could pull off something like that.