Sorry Lieutenant
Sure, an American like Rick O’Connell could serve in the French Foreign Legion. However, there’s something completely wrong about his rank. No, a foreigner cannot be a Lieutenant since officers must be French nationals in the Legion. Thus, he wouldn’t have been eligible for a commission.
Misleading Title
Yes, we know the name of the film, but the lead character actually doesn’t get mummified. You probably noticed this already. Of course, all the followers were mummified but the lead was victim to a different type of death.