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.
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.
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).
They sprayed Sam Lloyd with fake sweat after giving him a pasty looking makeover. After the pilot aired, his mother called him, worried about how ill he looked on television.