Orin: You'll be a dentist. / You have a talent for causing great pain! / Son, be a dentist. / People will pay you to be inhumane.
During the "Skid Row" number, Seymour goes all eighties-style music video, singing his solo ("Please won't somebody say I'll get out of here") while walking dramatically up to a chain-link fence. Just as he's about to finish it off by shaking the fence to demonstrate how caged and repressed he is, the camera turns around to show that there are a whole bunch of scary-looking hoboes trying to climb over the top. While singing a counter-verse to Seymour. He backs away very quickly.
At the end of the musical Seymour says "Thousands of you eating! That's what you had in mind all along isn't it?" and Audrey II responds with "Noooo shit Sherlock!".
Audrey II pantsing Seymour during "Mean Green Mother From Outer Space".
And all of his little bud chorus members.
Audrey II grabbing Seymour's gun and spinning it, and the little "Whoo!" sound he makes.
Late in the number, Audrey II cornering Seymour at a door, then a vine just missing Seymour's jewels. Both Audrey and Seymour's expressions were priceless.
Audrey II: I got killer buds / A power stem / Nasty thorns / And I'm using them! / So better move 'em out / Nature calls / You got the point? / I'm gonna bust your balls!
And then this line from Audrey II, before he explodes after Seymour electrocutes him with a wire:
"Oh, shit!" *KA-BOOM!*
When Seymour explains where he got the plant, his flashback/monologue turns into a music number with Crystal, Ronette and Chiffon providing background singing ("Da doo! Shoop da doo!"). Later, during his radio interview, he's asked the same question and begins to tell the story in the same words, cuing a chorus of "Da doo!" from offscreen. The scene changes.
Steve Martin mouthing other characters' lines during "Dentist".
Seymour getting the gun during "Mean Green Mother" and finding a tabletop paddle instead.
Frank Oz using his Fozzie Bear voice while directing.
"Excuse me, if you kids could just stop singing for a second?"
After Orin throws the masochistic patient out, calling him a "goddamn sicko", he makes to return to the room, but whirls around when he notices Seymour in the room, brandishing the scary dentist tool the masochist tried to take.
Orin: Let me ask you something! Does this scare you? Would you like if I took this and headed right for your damn incisors? It'd hurt, right?
Seymour: (looked scared and replying meekly) Uh huh.
Orin:You'd scream, right?
Seymour: Uh huh.
Orin: Well get your ass in here!
From the stage version, when Seymour goes to Orin's office to kill him:
Orin: Do you have an appointment? Seymour: I'm Seymour Krelborn, we met yesterday? Orin: Oh yeah, I remember you! The kid with the plant? Seymour: Right. Orin: And the Band-Aids? Seymour:(pulls out his gun) Right. Orin: ...And the gun? Seymour:(nervous) Right. Orin: Why are you pointing a gun at me, Seymour?
During "Feed Me (Git It)", Seymour and Audrey II start tapping their feet in unison during the song's closing lines. But since Audrey II has no feet, this consists of him bouncing up and down in his pot.