I found this most excellent site which describes a number of (presumably) real-world stories, wherein salepeople of various stripes encounter any number of humorous (and often self-inflicted) obstacles.  Here is a little taste:

“We drive back to the prospect's building and sit in the visitor's spot, mentally preparing and drinking frozen pop.

When we're ready to go I look over and his mouth, lips and tongue are BRIGHT GREEN - I mean really bright, like a clown.

Mine, of course were GLOWING RED”