When Caroline is sitting down in the dungeon on the Lockwood Estate and has blood on her mouth, the blood changes its consistency.
Stefan says Mason only has superhuman abilities during the full moon. However, at the carnival Stefan learned that Mason has superhuman strength even without a full moon when they arm wrestled, and Damon witnessed Mason's superhuman strength and agility when Mason fought a carny.
When Elena rushes down to the underground cells to try and save Stephan and Damon from Caroline's Mom and deputies, you'll see one of the uniformed deputies actually hisses at Elena at one point. The extra actor forgot he was playing a cop and not a vampire at that point.