When Frito and his girlfriend steal a car, they speed away from the scene so quickly that they visibly (and noisily) lose the right rear hubcap from the vehicle. But when they are shown speeding away from a gas station holdup shortly thereafter, a closeup of the right rear tire shows that hubcap in place. Then when they are being pursued on the highway toward the end, that hubcap is missing once again.
When McGarrett is on his way to the Changs' apartment he's driving his 1960s Mercury but he arrives in a 1970s model.
During McGarrett's voiceover about the guns used in assorted crimes, the dates listed on the tickets with the guns don't match the dates he gives in his narration.
When Danno investigates the shooting behind the bar the weather is dry. A few minutes later when he calls McGarrett the windshield of his car is all wet.
The gun that 5-0 is trying to find is a copy of a Beretta .25 semi-automatic. The clip holds 7 rounds but the gun fires at least 12 shots.
McGarrett knows Eddies last name without being told. Ellen only said his name was Eddie without saying his last name.
When the letter carrier is picking up the mail from the mailbox where the gun was found, the letters have postmarks. In postal boxes like this, all the letters are new deliveries from customers and would not have been processed through the post office yet.
When the box truck backs into the warehouse, it comes from out of a downpour, yet, as it comes to a stop inside, there's no dripping water coming off of it. The truck isn't wet at all.
Jack Lord blows his line when asking for "roadbocks" to be set up.