Group Gleefulness
http://sohoexperiment.blogspot.com/
One of my own favourite and most personally significant psychology experiments isn't an experiment at all in the strictest sense, more a set of observations. But it is scientific, it is fun and it was an impetus that steered me towards studying developmental psychology. I hope you find it delightful and intriguing too.
An ecological study of glee in small groups of preschool children.
There are many things I love about this study but to be brief. First, I love the image of all these groups of gleeful children. It's hard not to read the paper and imagine these delirious children without breaking into wide smiles yourself, which just goes to demonstrate how infectiousness glee can be! Then I love the fact that Lawrence Sherman had the inspiration to investigate something so cheerful and silly and I love that to do so he had to video hundreds of hours of lessons and then spend many hundreds of hours more carefully scoring and analysing the tapes to discover exactly how the phenomenon occurs. Science is a painstaking business, whatever your hypothesis. (Incidently, this study won it's author the Ig Nobel Prize for Psychology in 2001. Quite right too!)