Whoopee Trains?!?

The book "Railroading From The Rear End" by Farrington was published in 1946. A chapter on the B&M lists a lot of superlatives, including its use of special trains for special occasions. "Snow Trains" I've heard of, and "Hike trains" and "Barn Dance trains" are self explanatory. But it also lists "Whoopee Trains", and I'm sure it's NOT what came to my mind first So what WAS a "whoopee Train"?

All I can think of is the old Eddie Cantor song, "Makin' Whoopee", which details the lustier side of the male -female relationship. This probably involves copius amounts of alcohol stimulation, unless the trains were run during prohibition.