Task: Classify the mental state of the tweeter based on the tweet, determining if it is 'neutral or no emotion' or characterized by any of the provided emotions (anger, anticipation, disgust, fear, joy, love, optimism, pessimism, sadness, surprise, trust).
Tweet: Happy birthday to Stephen King, a man responsible for some of the best horror of the past 40 years... and a whole bunch of the worst.
This tweet contains emotions: 
joy