Trivia: Catherine Zeta Jones, after her fight with Zorro, her dress rips off. She turns around to grab the hat and you can see her nipple for one frame.
Continuity mistake: During the Alejandro/Elena fencing sequence, after he kisses her the first time, her left sleeve is down. The shots before and after have it covered. He slices the fabric off in the next shot. Her right sleeve also came down for no reason. (01:38:15)
Continuity mistake: When Antonio Banderas is finally proficient at swordsmanship, he knocks Anthony Hopkins' sword out of his hand and catches it. He then laughs and throws it back pointing downwards, but when Anthony Hopkins catches it, it's pointing upwards. (00:41:00)
Continuity mistake: When Alejandro and Diego fight in the cantina, Alejandro knocks over stalks of corn rolled up in a bundle into the doorway. In the next shot, the corn stalks are standing again. (00:35:30)
Deliberate mistake: During Alejandro and Elena's duel, he slashes her skirt and reveals her bare leg. When he slashes off her whole gown, she's somehow wearing leggings. Obviously so Catherine Zeta-Jones would not be naked. (01:38:13 - 01:39:20)
Continuity mistake: When Three Finger Jack presents Alejandro and Joaquin to the bumbling Mexican soldiers, he touches a wanted poster and asks permission to read it. He's not touching it any more in the next shot.
Answer: Marc Antony and Tina Arena sang it. Lyrics at http://www.lyrics.net/lyric/5746519.
Hobbes