Continuity mistake: At the beginning of the film, Casey is cooking popcorn on the stove. When she peels the top off, you see her peel the side away from the handle, and she's using her left hand, but when the shot changes, she's using her right hand, and is pulling from the other side. (00:01:15)
Continuity mistake: When Casey is making popcorn, firstly the top of the popcorn that she tears off and places next to the stove changes from being folded in half, to later on laying down flat. Secondly Casey picks up a salt shaker and places it by the stove, but this later disappears. (00:01:25 - 00:03:30)
Continuity mistake: In the opening scene, Drew Barrymore put the Jiffy Pop on and it sizzled right away. In reality, it takes about ten minutes to heat up. And also she should have shaken it when it started sizzling. (00:01:25)
Continuity mistake: If you look at the close-up of Casey's hands when she locks the door, you can see her left arm in frame, but in the next shot she is holding the phone to her ear with it. Later on there's a mistake even more blatant as she unlocks momentarily the patio door to check on Steve; in close-up she uses her right hand, the killer reprimands her for the stupidity of the move, and she pulls back her left hand, as the right hand is once again the phone hand. (00:02:55 - 00:05:45)
Visible crew/equipment: When Casey tells the killer "Dial somebody else, okay?", you can see the shadow of some equipment on the decorative pillar at the top right of the screen as the camera moves backward. (00:03:18)
Visible crew/equipment: When Drew Barrymore runs away after the killer just called her 'blondie', there's nobody behind her character, and yet a new shadow is cast on the wall to the left when the camera follows her around the corner to lock the front door. (00:03:50)
Audio problem: When Steve is on the porch and gagged, the killer instructs Casey to turn off the lights. Steve shakes his head and lets out some muffled 'No's. When the lights go out he says one last 'No' but you can still tell he isn't saying it. Even though his mouth is gagged, he makes no body movements to correlate with his shouts like he did before, especially not his jaw. Despite it being dark you can still tell. (00:06:10)
Visible crew/equipment: When Casey agrees to play the killer's game she crouches down next to the television and as the killer says "Here's how we play..." you can see a clear shadow of the head of the boom microphone cast on the white wooden railing at the top right of the screen. (00:06:25)
Continuity mistake: There's a close-up of Drew Barrymore's foot when she unplugs the lights when the killer is starting his trivia. She tosses the cable and plug blindly behind her. In the next shot, the plug is closer to her foot and the shadow resulting from the change in light is also different. (00:06:25)
Continuity mistake: When Casey puts the two videos on top of the TV, she puts them on top of each other so they are placed neatly. Then when she picks up the letter opener off the TV later, the videos are no longer stacked neatly. (00:08:10)
Suggested correction: To be fair, we don't see (at least in the DVD version I am looking at?) the VHS boxes for the entirety of the time her hand is on it, and she does bump against the TV set at least twice while talking to the killer, once with the top of the set entirely off-camera.
I would say it's a valid mistake because we do see a shot of the tapes later, and they're still neatly placed (for example, when she says her boyfriend will be there any second), so we know she didn't do anything to them when her hand was off camera. And I never saw any bump hard enough after her boyfriend is killed that would move the top case into the new position it's in.
Continuity mistake: When Casey peeks at the letter opener on top of the TV, her hair is on top of the cordless phone; in the shots from the side, before and after, her wig is pressed against her cheek and ear by the phone itself. (00:08:40)
Continuity mistake: When Drew Barrymore is running to the kitchen after the patio windows break she grabs a knife. When they show her going through the doors from the inside to go outside her knife's curving blade is pointing toward the celling but when the show her leaving the house through the doors from the outside the knife curve blade is pointing down. (00:09:25)
Revealing mistake: As Drew Barrymore is running from the killer outside he stabs her. If you look closely it is very easy to tell it is a rubber knife, because you see it bend off of her. (00:10:20)
Continuity mistake: When Casey pops up to peek at the window and is face to face with the killer, she shakes with fear reacting very naturally, but in its close-up her left arm is sticking out perfectly steady and firm in an incredibly unnatural position, blatantly there holding still just so the killer can grab it. (00:10:20)
Continuity mistake: The first time that Casey Becker is stabbed by the ghostface, you can see the knife go into her chest, very deeply, but no blood is there, but directly in the next shot, her shirt is covered in blood. (00:10:50)
Continuity mistake: After Casey has been stabbed in the chest she falls down and the killer gets on top of her, before he can stab her again she knocks the knife out of his hand and the killer instead starts to strangle her. She then kicks him off her but you can see he still has the knife in one of his hands as he falls backwards. (00:11:00)
Continuity mistake: In the close-up when she clutches Ghostface's mask, Casey's hand is significantly bloodier than in the rest of the scene and the sleeve that was creased down straightened itself, with a different bloodstain. (00:11:35)
Audio problem: Casey's dad tells his wife to call the police. Meanwhile, he runs upstairs yelling "Casey, are you upstairs?" He reacts to his wife's line turning towards her before she says "Casey, baby?" (the mother does whisper "My God" a moment before he stops and turns too, but it was a whisper, good luck hearing that when he was rushing upstairs and shouting his line). (00:12:10)
Continuity mistake: After the girl's dad leaves the room, Billy holds up a red stuffed bear against the bed. In this shot, the bear is only half sticking up at about its arm level, but in the next cut, it's high enough its feet are visible on the bed. Then only a second later as Billy starts to stand up, a jump cut has his arms go from down to outstretched with the bear instantly as he starts to stand. (00:14:10)
Revealing mistake: Sidney is teasing Billy, and as a sort-of-reward to him she flashes him before he goes. That's the idea, but in the view from behind you can actually see through the nightie the shoulderstrap of a bra. (00:16:55)
Suggested correction: Could she have had a bra that undoes at the front and quickly flashed him?
To actually answer the question; her hand is on full display, holding the nightie open. She'd still have to open the bra. You can technically argue that you can't see her other hand, which she could be simultaneously maneuver to pull down the cup of the bra and expose a nipple, since there's hardly any time to undo it fully and she'd have to fasten it back afterwards. Or that cupless bras exist. Truth is, she opens her casual, normal, comfy nightwear during the unexpected visit of her boyfriend, and the way the scene is shot leaves no room to interpretation.
This is a question, not a correction.
