I've done this a few times and it's a lot of fun! You can't have a bad day after going to laughter yoga. It's nothing like regular yoga, so dress comfortably. You basically act like a 5 year old for a solid hour. It's awesome.
From their website: "In Laughter Yoga, we laugh for no reason, without jokes or comedy and even if we don’t have a sense of humor. The laughter comes from inside ourselves rather than from an external source so we’re not dependent on someone or something to laugh.
As adults, we typically laugh from our heads when we “think” something is funny or we’re laughing “at” someone, rather than from our hearts and souls like children do. In Laughter Yoga we rediscover the childlike laughter that emanates from our hearts and souls and not our heads."