Oliver Queen aka Green Arrow makes his first appearance. Green Arrow is a fictional character, a superhero that appears in DC Comics.
Clark Kent discovers his superbreath abilities for the first time.
At the beginning of the episode, you hear a newscast about Dark Thursday, if you continue to listen (as Clark walks in), you will hear the reporter say, "This is Genevieve Sparling reporting live." Genevieve Sparling is a writer's assistant on Smallville.
When Chloe brings the kite into Clarke's barn, it is the shape of the classic superman symbol.
It is unexplained why Clark's super breath is not weakened like his other powers. However, it is possible that being a new power, Clark lacks the usual self-control over it and uses more force than he would normally exert.