J.D. is loosely based on a real person and a lot of the situations the character faces are based on real-life moments the real J.D. had to face, including having nurses do his hypodermic procedures and IVs.
Elliot's character was originally written to be mean-spirited and opportunist; after careful consideration, the producers realized that Elliot's character wasn't sympathetic or likable, and therefore re-wrote and re-shot some of her scenes. This is why Elliot seems out of character in the pilot.
Turk uses the electrical defibrillation paddles to "shock" an apparently unconscious patient, who immediately wakes up screaming in pain, apparently not having been unconscious at all. That patient was played by Vinko Bogataj, the Slovenian ski jumper whose disastrously unsuccessful ski jump attempt was made famous in the opening title sequence of ABC's television sport news show ABC's Wide World of Sports (1961).
While 'Scrubs'' "regular episodes" are shot at the former North Hollywood Medical Center, The Pilot episode was filmed in another hospital in Glendale, California which, incidentally, has since been torn down. Some of the scenes in this episode had to be reshot in North Hollywood, though, making the continuity of this episode somewhat difficult for the crew.