It's a sad, sad day when this is the reason people are being arrested.

A group of young Iranians have been arrested for dancing in a YouTube clip set to Pharrell Williams’ Happy.

As in the singer’s original video, the Iranian fan version features a series of young men and women dancing to the hit song in a variety of settings.

The six young men and women were reportedly arrested on Tuesday under deceptive — and seemingly mysterious — circumstances. IranWire reports:

All of the young producers received phone calls informing them that a friend had suffered a car accident and required their help. When they arrived at the address they had been given over the phone, security forces were waiting to arrest them. Security forces have also allegedly threatened the families of those arrested that if they speak to any media about the detention, their children will not be released.

The video, filmed on the streets of Tehran, was one of the many videos created by fans of the song across the world in response to the catchy tune about the universality of joy.

Happy featured in children’s film Despicable Me 2 and was nominated for Best Original Song at the Academy Awards earlier this year.

Pharrell himself also posted a link on his Twitter to a story about the arrests, saying, “It’s beyond sad these kids were arrested for trying to spread happiness.”

While the arrested youths were released overnight after a Twitter campaign with the hashtag #FreeHappyIranians, the International Campaign for Human Rights in Iran said the director of the video was not released.

Some more photos of the group…