The line comes from Michael Scott, the regional manager played by Steve Carell in the American version of The Office. Scott's exaggerated optimism and desperate need to be liked made short bursts of his enthusiasm easy to lift as standalone reactions. Clips of his approval spread on meme pages and in edited videos because the meaning is clear even without the original scene. It remains popular as a wholesome, positive alternative to sarcastic reactions, used whenever creators want approval to sound genuine, funny and a little overblown.