"Do you have any idea how ridiculous you sound? Just because you put a strange and interesting plant in the window, people don't suddenly—" "Excuse me, I couldn't help noticing that strange and interesting plant. What is it?"
The scene where Seymour is at the radio station to be interviewed, and the plant, Audrey II, tries to bite that lady's butt, but Seymour stops it from doing so.
The subsequent interview by WEIRD! radio DJ Wink Wilkinson, played by John Candy.
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. He backs away very quickly.
Audrey II pantsing Seymour during "Mean Green Mother From Outer Space".
Audrey II cornering Seymour at a door, then a vine hitting Seymour's jewels. Both Audrey and Seymour's expressions were priceless.
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?