8 Movies That Completely Ignored Important Plot Points
4. Harry Potter And The Chamber Of Secrets - Crabbe And Goyle's Weirdness
Malfoy's henchmen Crabbe and Goyle are meant to be pretty stupid, but an unresolved situation in Chamber Of Secrets makes them (and Malfoy) seem ignorant and stupid beyond belief.
Midway through the movie, Harry and Ron take a swig of Polyjuice Potion to transform into Crabbe and Goyle, leaving the real Crabbe and Goyle unconscious in a closet. They then proceed to the Slytherin common room, where they have a conversation with Malfoy about the opening of the Chamber and the Heir of Slytherin.
Malfoy notes that they're acting oddly (they also sound like Harry and Ron, something that's never brought up), and the scene ends with the disguised Harry and Ron hastily fleeing the common room as the potion begins to wear off.
After this, we're led to believe that Malfoy, Crabbe and Goyle never brought their conversation (and this strange behaviour) up again.
So Malfoy never asked his real friends why they were acting so weirdly? Crabbe and Goyle never told Malfoy that they were stuck in a closet at the time he supposedly had a chat with them in the common room? Simply mentioning either of these things would reveal to Malfoy that he'd been talking to two impersonators, an important point that could have affected the rest of the plot.
From here, he could have deduced that Harry, Ron and Hermione were to blame, which could've led to some serious trouble for the Gryffindor trio (to brew the potion they needed to steal ingredients, just one of the offences they committed) and impacted their mission to stop the Basilisk.