Audio problem: When Dean puts the cassette in the car stereo he reads 'Metallica' off it, yet AC/DC plays. [In the original version Metallica was played, but AC/DC was used in newer versions due to copyright issues.]
Continuity mistake: Dean circles the newspaper article on Sophia Carlton. When he hands it to Sam the circle is different. (00:03:20)
Continuity mistake: When the Carlton son reaches in to pull the plug out of the sink you can see the plug chain on the cutting board to the left of the sink before he even reaches in, then he pulls it out and puts the plug chain on the board. (00:14:30)
Visible crew/equipment: Before The End of the episode, Sam and Dean are thanked by the sheriff's daughter and her son. When Sam and the mother are left alone, his microphone wire is visible when he stretches. (00:41:00)
Continuity mistake: When the girl is taking a bath, the water is so full that its almost overflowing. She gets into the tub and the water doesn't overflow. The faucet is still running and yet the water keeps changing from full to down below her shoulders.
Revealing mistake: When Sam pulls Angela out of the bathtub and on to the floor, you can see the panty line from the nude colored panties she's wearing to keep the show PG13.
Audio problem: The pilot asks Amanda how she is at the start. When Amanda replies the audio doesn't match her mouth. (00:02:10)
Continuity mistake: In the scene where the passengers board the plane at the beginning, the aircraft is a Boeing 737, noticeable by the crew jumpseats located by the entrance door. But the first scene you see where the aircraft is in flight, the aircraft changes to a Widebody Airbus, possibly an A310, noticeable by the different style of winglets that Airbus uses compared to that of Boeing. (00:02:15)
Continuity mistake: At the start as we see the victim on the plane, we see a blonde woman sat in the middle seat 2 rows in front of his row. When he gets up to stretch his legs, this blonde woman has now changed to a Chinese one. (00:02:45)
Continuity mistake: When the first victim stands up to stretch his legs, he grabs the seat in front of him and his arm is bent. When the shot changes his arm is now straight and he's holding the middle of the seat not the edge. (00:03:00)
Continuity mistake: When Dean says he's going to talk to Amanda to get a grip on her mental state he has his head back on the seat and is looking straight ahead. When the shot changes he's now looking at Sam. (00:27:20)
Bloody Mary - S1-E5
Continuity mistake: When Sam and Dean enter the Shoemaker home, a woman leaning against a wall holding a coffee cup starts to follow them down the hall. When the shot changes, the woman is back against the wall, talking to someone who wasn't there in the previous shot. (00:08:00)
Bloody Mary - S1-E5
Continuity mistake: When the real Jill is being Killed the blood lines from her eyes go from smeared to "clean" lines instantly. (00:14:20)
Bloody Mary - S1-E5
Continuity mistake: In the scene where Jill is looking at her 'Bloody Mary' reflection, the lines of blood coming from her eyes go down and straight over her mouth (because she hasn't smeared them like the real Jill has). But as she begins to talk, the lines switch from being over her mouth to off to either side of her mouth and back multiple times. (00:14:20)
Bloody Mary - S1-E5
Continuity mistake: When Jill's friend is saying how Jill died and mentions her eyes, she has her hands lowered in one shot but raised in the next. (00:16:11)
Bloody Mary - S1-E5
Continuity mistake: When Sam is looking at the mirrors with night vision, we see him pause and say to Dean "Look at this." The camera then cuts to an extreme closeup of the camcorder screen and the image on the screen is different to what was on there before. (00:18:15)
Continuity mistake: During the scene where Sam is tied up and eventually fights the fake-Dean in Becka's house, there is a shot that shows both his feet and hands tied. During the fight, both his hands and feet are shown free, but he only cut free his hands, and began fighting immediately after that. (00:25:20 - 00:25:55)
Answer: Angel blades come from angels. It's their angelic magic that makes it special. Therefore, an archangel blade is made magical with the powers of an archangel. They couldn't have just created one or used one, as none of them are archangels.