Continuity mistake: When Seymour tries to kill the plant he pulls a gun, the gun is a six shooter, the plant grabs the gun and fires at the guy, then he fires some more, in total the plant fires 9 shots with a six shooter...
Continuity mistake: Look carefully at Rick Moranis' mouth throughout the movie- he goes from having braces on his teeth to not having them, especially in scenes where he has to sing and they would have messed up his enunciation.
Continuity mistake: In "Suppertime" (reprise) the inside of Audrey II's mouth is a vibrant purple, but during "Mean Green Mother" it is a fleshy pink.
Continuity mistake: When Audrey 2 calls Audrey (just before she gets 'eaten'), a piece of hair is in front of the phone. Then it zooms in and all her hair is behind the phone.
Continuity mistake: When Seymour is in the waiting room, holding Audrey II, the plants tongue reaches for the woman bending over and the tongue is bright yellow. At other times it is red.
Continuity mistake: When Seymour has just met Orin, DDS, when Audrey and Orin are leaving on a motorcycle, and Orin asks, "You got the handcuffs?" you can see that he would have to turn right to go down the alley, but in the next shot, he just goes straight.
Answer: He says "and a success". He's singing about his mother telling him he'd become a successful dentist.