Jensen Ackles, who played Jason Teague in season four, was the second choice to play Clark Kent. If Tom Welling had not accepted the part, the role would have gone to him
According to DVD commentary, Tom Welling was known to wander around the set muttering under his breath, "Clark is an idiot! He is such an idiot!"
Tom Welling (Clark Kent) and Allison Mack (Chloe Sullivan) are the only actors to appear in all ten seasons.
In each episode, Clark Kent (Tom Welling) can be seen wearing any one of, or a combination of red, yellow, and blue; the colors he will one day don as Superman.