Yes he is. But it was actually Dylan O'Brien messing around so it's from the season 1 gag reel (the bloopers).
The scene they were filming is from the episode 1x04 "Magic Bullet". It was at the animal clinic, right after Derek healed himself with the bullet Scott brought from Kate Argent's bag (towards the end of the episode).
Check around 0:20 in this video to see the blooper ;).