A very easy song. If you know the tune to Pop Goes the Weasel, then you can do it. Split the audience into about 3 groups, and they la la to the afore mentioned tune. At the end the last 3 syllables are not la la`d but are replaced with a very loud

Whoops LA LA LA LA with a bit of a Mexican wave type leap in the air. After a couple of practices, start it off as a round. The next group starts when the previous group is on their second line as follows.

La la la la la li la la,
La la la li la la (group 2 start when group 1 start this line)
LA la la la la li la la
WHOOPS la la la la!