Arsène Lupin III

Arsène Lupin III is the main character of Lupin the 3rd and a special only deuteragonist of Detective Conan.

Background
Lupin III is the grandson of Arsène Lupin, the famous French gentleman thief.

Lupin the 3rd vs. Detective Conan: The Movie
Lupin makes a return in the story by disguising himself as Kid the Phantom Thief to steal a diamond as part of a test set by Alan Smithee.

Trivia

 * While Lupin hasn't officially appeared in Detective Conan, during the Jolly Roger special, there was a robber who disguised himself as Lupin.
 * He was never named "Arsène" in Japanese media, the only partial exception was Lupin the Third Part 5 where in The Girl in the Twin Towers his profile was listed in that name in English.