Luke is in the 1st film level 2 there is a part where you can fall down and you will be near a cave with luke upside down use explosives to get him down.

Go to Raiders of The Lost Ark: Into the Mountains
Santa Clause: Go to the house near the ponies. Use an Enemy Officer (the one with the bottle bomb) and knock on the door where the guard is. One he accepted you, go inside, break things to find clues. When you had finished, Santa Clause will come down the chimney. (When you turn on the "Secret Characters" parcel and go back to
"Into the Mountains" and you could use Santa Clause.)

Luke Skywalker: Go more further the mission, "Into the Mountains" and look for a long string<---the thing you climb with. <-- And go down. Luke is placed upside down in an icey cave. Use an Enemy Officer and throw the bottle bomb to put him down.
<|> He wouldn't die of course<|>

Chewbacca is the final Star Wars Character in the game, he is in the Raiders Of The Lost Ark in the Third Level. He is inside the cantina with the parcel for that level. Note: You will need a small character to get him.