Toward the end of the game, Mario and company are attempting to rescue Peach from Bowletta. Fortunately, Toadsworth had packed an extra dress for Peach in case of Clothing Damage. Mario's solution? Dress Luigi as Peach, then attempt to pass him off as the "real" princess. Luigi goes the extra mile; he mimics Peach's voice with surprising accuracy, and even covers his face with his hands to hide his mustache...until he is in Bowletta's cruiser.
Bowletta: By the way, Princess...why are you covering your mouth with your hands?
Fawful: Do you hide something?
Bowletta fakes Luigi out, and Luigi uncovers his face.
Bowletta: Fawful...did you see that?''
Fawful: Yes. Mustache.
Bowletta: ...fire at will.