Revealing mistake: When Blade shoots Quinn with a silver like dart, Quinn gets thrown back, and the wall behind Quinn bends when he hits. Then Quinn (stunt double?) bounces off the wall instead of being stapled to it. (00:09:10)
Revealing mistake: When Karen and Whistler start to fire at Frost's men, after they discovered Blade's hideout, Whistler shoots a black guy who has a large bump under his shirt, quite obviously the squib. (01:11:00)
Revealing mistake: In the final fight scene, Blade is fighting a bunch of guys. Before the shot goes to Karen looking down at Blade, Blade kicks a guy away, you can see the stunt wire pulling him back. (01:43:05)
Revealing mistake: When Blade uses his booby-trapped sword to knock down the serum from the wall at the end of the movie, you can tell the zoom in of the shot was sped up, as the rotating-timer-thing is spinning quicker than normal, and the screen is vibrating quickly.
Revealing mistake: When Blade is fighting Frost's men near the end, Blade kicks an Asian man to the ground. When he hits the ground, you see he hits some sort of mat or pillow under the dirt.
Revealing mistake: When Blade is being put into the chamber so they can siphon his blood, there are straps for his neck and his wrists. He is placed into the chamber and his hands are placed in the wrist restraints, no one reaches for the neck restraint. In the next scene, the strap is around his neck.
Revealing mistake: When Traci Lords approaches Blade, he tries to shoot her with the shotgun only for it to click, empty. He then proceeds to impale her with the silver stakes mounted in the end of his gun. If you look closely (probably more noticeable in full screen), you can still see the tips on the end of his stakes when she hisses at him, meaning that they're not actually inside her, even though she disintegrates in the next shot as if they were.
Revealing mistake: When Quinn is pushing through the door after Blade has cut his arm off, the full length of the arm is visible as he pushes the door open. On the other side of the door, his arm is gone again.
Answer: I don't think it's so much a memory as it is Blade just equating Karen with his mother in that moment. The only way to convey his thought process to the audience, though, is to show his mother onscreen.
Phaneron