Hot Dog Vendor
The hot dog vendor worked at the airfield Derek Maza was flying a glider he had just bought. Elisa asked the vendor for a hot dog with everything on it in the form of an old joke. The hot dog vendor had heard it before. When Elisa said she was looking for Derek, the hot dog vendor immediately figured out she was Derek's sister since he had mentioned she would be coming by.
Nothing else is known about the hot dog vendor. It can be assumed he was acquainted with Derek because the latter mentioned that Elisa was coming. The hot dog vendor’s default facial expression was a surly one.
Elisa only tells half the joke. The full joke is:
What did the Zen Master say to the hot dog vendor? "Make me one with everything." The Zen Master handed the vendor a $50 bill for a $2 hot dog. The Zen Master was munching on his hot dog when realized he hadn’t received any money back. “What about my change?” he asked the hot dog vendor. “Change comes from within”, the hot dog vendor replied.