Joy, like Sadness, Anger, and Fear serves survival functions.

When these emotions detract from beneficial thought and social functions are when they become the norm instead of the exception.

People who are addicted to joy will uncontrollably seek out exciting, and often dangerous activities, to get the rush.

Individually, they love to listen to and tell over-the-top jokes, especially those that involve illogical punchlines that require lateral thought connections.

"What kind of bus can stand on a sidewalk? A busker"

Many of the individual activities are harmless to others whole providing pleasure to only the Joyeur.
Unfortunately, when a small percentage gets bored of them, they resort to getting their rushes elsewhere, more commonly practical jokes or pranks. This is when Joy becomes Wickedness instead.

Pranks have a very little upside for the prankee, which embarrasses and in some cases, even injures them. Conversely, there is always an upside for the Wicked.

Most Joyeurs won't cross this line. But the Wicked will demolish it.

Children, at early age, learn it from family and friends, laughing at minor accidents at home or at school.

Also, watching cartoons where the heroes laugh at the villains' boss berating his henchmen for once again causing his failure.

Parents might find this behavior cute, but unclarified, uncorrected, and unguided, it could lead to an addiction that lasts a lifetime and affects many other people in the years to come.

It could even lead to the dreaded output of wickedness: bullying.

Wickedness is not funny.

Nip it in the bud. Fast.