Character mistake: In the scene where John Spartan goes into the sewers, he has a conversation with a Spanish-speaking woman. At the end of their conversation the woman says "Gracias" (correct Spanish) to which Spartan replies "Prego", which is Italian. Up until that point Spartan spoke perfect Spanish. (01:23:30)
Character mistake: When the alarms go off in the police station indicating the code 187 all the police officers are confused as to what is going on since they know nothing of MDKs. Zack Lamb should have already known what the code meant, yet he never says anything and just waits for everyone to figure it out.
Suggested correction: I took it as he went into almost shock that after so many years a murder had actually taken place. He says, "I don't believe it," indicating he knew what the code meant but then he kind of froze until Phoenix's name was mentioned.
Suggested correction: Zack Lamb is quite old and it's possible he simply forgot what the code meant. He was a pilot too, not a street cop.
When Stallone first meets Lamb after being thawed in the future, he tells Spartan he was "grounded" after the events in the opening scene so had not been a pilot for 36 years.
