An old saw declares that laughter is contagious. My girlfriend and I went to the Drake Public library yesterday, (where she is denied a free library card, even though I have one and we live less than two miles apart) and got into a giggle session as we compared titles and discussed the "finds" she'd gleaned from the book nook shelf area, titles being culled from the collection.
Soon a smiling lady joined us, introduced herself, and invited us to join the Friends of the Library group, by the president herself... We were both pushovers...
I've noticed that when my sister and I got the giggles calling each other to see various swaths of cloth in a fabric shop, the same thing happened... people spontaneously talked to us, laughed with us, and everyone within hearing began to smile. (We were NOT asked to join anything with or without dues attached, however.)
This phenomenon appears to be age/gender independent. A 20 something male friend and I set each other off by offering each other inappropriate or comic book titles, carrying on clear to the checkout counter, where two clerks manned dueling cash registers side by side, back to back with another set. He calmly announced that I was his parole officer when a remark about a possible mother/son connection was made.
Shoe stores, restaurants, walking down the street, standing in thirty minute or more lines to use the rest rooms in a Disney park -- the venue seems not to matter. Fun is where the heart is.