Provenance - S1-E19
Other mistake: In the scene where Sam, Dean and Sarah go to compare the painting to the earlier photo of it, Dean, noticing the changed position of the razor, says, "Jared, check it out." He is speaking to the character Sam. The actor's name is Jared. [Confirmed in cast interviews].
Other mistake: When Dean is listening to Sam's voice mails that he left while in Gary's body, the voice in the recordings are of Sam. If Sam was in Gary's body, they would have been of Gary's voice.
Other mistake: In the final scene the ECG reads in the bottom right corner of the monitor 09:06:12 19 JUL 06. When the Dr. Calls time of death he states 10:41am.
Back and to the Future - S15-E1
Other mistake: After the spell is cast, the ghosts are chasing Sam, Cas, the mom and the girl towards the safety line...despite ghosts being able to teleport themselves short distances, as they were doing only minutes earlier. They could easily have jumped ahead of them, instead they gave chase on foot.
Tall Tales - S2-E15
Other mistake: When Dean is telling the Trickster that he likes his style it shows the same shot of Dean twice saying "I do, I mean..."
Other mistake: When Dean is having fun with the Magic Fingers and listening to music, the song displayed says Led Zepplin - Kashmir. Further listening proves it to not be Zepplin at all. (00:05:45 - 00:06:30)
Other mistake: In the original "Scooby-Doo" episode from which this episode is taken from, the house for the reading of the will was on an island as the Mystery, Inc. gang travelled to the house via motorboat. In this episode of "Supernatural", Sam, Dean, and the Mystery, Inc. Crew merely drive up to the house.
Other mistake: Dean is tied to a chair when Sam rescues him. His hands are tied to the arms of the chair with rope. Sam comes over and just casually loosens the rope and it comes right off, then Dean just simply flings the rope off the other hand like they weren't even tied up, Yet before Sam got there, Dean was struggling to get loose.
Other mistake: When the guy goes to room 1444, the door slams behind him. He doesn't even try to open the door. He just shakes the door knob.
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.