Other mistake: When Eddie reads Kasady's letter, it's obvious that the whole speech can't fit inside the postcard. Moreover, parts of it don't even make sense since Eddie could never "see" the part about Shriek; he knows nothing about her at that point of the movie. Finally, either way when we see him read the letter, the parts shown don't match the narration; for instance when he gets to the part about Kasady's heart stopping, it is on the part of the postcard opposite of the one he's 'reading'. (00:24:25)
Other mistake: Venom and Eddie are having a domestic dispute. Items rain off the window in front of a homeless person. The other passers-by change between shots. Not only that; in the second shot there's one extra who turns around acting startled by the man's shout. Does not really make sense; heavy objects just crashed down a few feet from him, anyone would have been startled by that first and foremost. Wrong reaction time/ direction of the extras. (00:32:45)
Other mistake: Eddie witnesses in horror from the window his former alien partner wrecking his Ducati bike in the alley below. Venom exits stage right and possesses a lady riding a bicycle, headed towards his right. Somehow, this double *right* turn leads to Eddie witnessing Venom's middle finger from a window to the *left* of his original position. (00:34:30)
Other mistake: In a weird move concocted for the movie, Carnage creates a tornado spinning around real fast with his tentacle sticking out. Against physics, one of the tentacles gets a hold of the prison chief and keep still for a few seconds while Carnage's body in the background has spun around itself a few times already. (00:38:30)
Other mistake: Dr. Pazzo (which literally means "Dr. Mad" in Italian, incidentally) turns towards the computer with the voice synthesizer before the phrase is spoken. (00:51:20)
Other mistake: When Casady crushes Shriek's cell, they both have their hands on the glass wall that gets shattered, nothing protects them, and yet she has her hands all over him to passionately make out - the shattered glass is like it never existed. (00:52:30)
Other mistake: In the comics it is always very clear that the clothes Venom and Carnage appear to be wearing are shapes the symbiotes take and not actual clothes. In the movie, Eddie wears his own clothes, and so does Kasady, since we literally see him stealing the flamboyant outfit from some guy, and the clothes stay solid even when the symbiote is incapacitated. In that case, it makes no sense that the clothes at no point get damaged when they get stabbed or even torn open like it often happens in the movie.
Other mistake: Kasady kills Dr. Pazzo hanging/strangling her with one of his tentacles coming from above. When you look at the section Frances was held in though, and considering the moderate speed the tentacles showed in their slithering while on camera, there's no way they could have reached her in time - that without mentioning the fact that Kasady himself appears inside the cell with no explanation - if he was already there by hacking, it does not explain the movement in foreground at the beginning of the scene.
Other mistake: In the end credits, Christopher Godwin is credited as "Headmaster (1997). " The scene when he appears had as caption "St. Estes Reform School - California 1996."
Other mistake: At the beginning of the movie, Shriek reads an article mentioning that Cletus' story is "coming to an end", and Eddie is credited with uncovering "what the FBI and police could not " That doesn't fit with Eddie supposedly down on his luck and badly needing a scoop; and in fact the tagline is the same that will appear in printed and audio news later when Eddie does rise to fame again by discovering the bodies. Also, the article talks about Eddie Brock, but somehow is WRITTEN BY Eddie Brock.
Answer: It is deliberately never shown on screen, so unless it gets answered in a sequel the audience is left to speculate. Mulligan does come into direct contact with Carnage since Cletus is the person who kidnapped him. In addition, the fight between Venom and Carnage takes place all over the church with the pair constantly stabbing, slashing, and bludgeoning each other. A piece of either symbiote could be somewhere in that building. Again, though this is just speculation since it's never shown how Mulligan is infected.
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