The Wonderfully Weird World of Gumball - The Entrance (leaked animation)
Someone on the Gumball subreddit posted this and Ben himself replied to it with "That's what we call a leak in my profession."
It's not known what episode this is from. UPDATE: blurred out animator's name to avoid them getting in trouble. DOUBLE UPDATE: This is from The Entrance, the 12th episode of the new season.