Did you know that June 12 every year is Superman Day? We're not sure how this particular day came to be dedicated to the Man of Steel, especially since he seems omnipresent in our lives every day. A pop cultural mainstay since 1938, the Krypton-born hero never seems far away, especially in the movies.

Yet while it seems every boy has dreamed of putting on the red cape and flying, the character has been remarkably hard to cast in movies. For every Christopher Reeve, Brandon Routh or Henry Cavill who said yes, many more have said no. Here are 15 potential Kal-El's that never came to be.

1. Sylvester Stallone
"Yo, Lois!" After the success of "Rocky," it's no wonder that "Superman: The Movie" producers Alexander and Ilya Salkind considered Stallone to play the Last Son of Krypton. Reportedly, he was deemed too ethnic for the part, though other sources have said that Marlon Brando (who was cast earlier as Superman's father, Jor-El) refused to work with him.

2. Ben Affleck
The future Batman was once Supes. When producer Jon Peters hired Kevin Smith to rewrite the script for proposed 1990s reboot "Superman Lives," the writer-director and comics fan envisioned his "Chasing Amy" star in the lead role. But when Tim Burton was hired to direct, he had Smith's script rewritten and tossed out his casting ideas.

3. Neil Diamond
Yes, the rumble-voiced crooner was on the short list of performers that the Salkinds considered for Supes, even though he had no acting experience. Diamond reportedly turned down the role when he realized he could make more money if he spent 1977 touring. His "Superman" screen test is lost to history, though it may have sounded like this.

4. Robert Redford
Redford had been playing men of action for a decade (in such movies as "Butch Cassidy and the Sundance Kid" and "Three Days of the Condor") when the Salkinds approached him to play Superman. But he said no, explaining, "Nobody is going to believe me flying." (He also reportedly balked at the money and the lack of a completed script.)

5. Warren Beatty
Asked by the Salkinds to consider playing Superman, "Shampoo" star Beatty got as far as taking the suit home for the weekend. He brought it back on Monday, saying he felt he looked ridiculous, and declined the part.

6. Patrick Wayne
The Salkinds actually offered John Wayne's son the role of Superman, but he turned it down to look after his father, then newly diagnosed with stomach cancer. The younger Wayne did go on to star in action films "Sinbad and the Eye of the Tiger" and "The People That Time Forgot."

7. Muhammad Ali
The boxing champ had no acting experience, but his charisma, physique, fighting skills, and worldwide fan base helped put him on the short list for Warners' first Superman movie. Producer Alexander Salkind was almost ready to cast Ali until Salkind's son, Ilya, pointed out that Ali was black. Ali did manage to appear in the 1978 comic book, "Superman vs. Muhammad Ali." And yes, The Greatest does knock out the Man of Steel.

8. Jon Voight
The "Midnight Cowboy" star was one of many A-listers whom the Salkinds considered to play Clark Kent. Among the others on their list: Voight's "Deliverance" costar Burt Reynolds, Voight's "Midnight Cowboy" costar Dustin Hoffman (who nixed the roles of both Clark Kent and Lex Luthor), Paul Newman (who declined the roles of Superman, Luthor, and Jor-El), Steve McQueen and Clint Eastwood.

9. Nicolas Cage
Cage is such a Superfan, he named his son Kal-El. In Tim Burton's aborted "Superman Lives," Cage would have played a revisionist version of the character; he was even fitted for a black-and-silver version of the Superman costume (that lit up!) and cashed a check for $20 million before Warner Bros. scrapped the project.

10. Will Smith
After Nicolas Cage and Tim Burton dropped out of "Superman Lives," producer Jon Peters tried to resurrect the project with a newly-revised script and offered the role to his "Wild Wild West" star, Smith. Mindful of the backlash he'd received for playing a character who was white on TV, Smith demurred. Years later, Smith recalled: "There is no way I'm playing Superman!' Because I had already done Jim West, and you can't be messing up white people's heroes in Hollywood!" He ended up playing an original screen superhero instead in "Hancock."

11. Josh Hartnett
Up for the role in two separate films -- Wolfgang Petersen's aborted "Batman vs. Superman" and the "Flyby" project written by J.J. Abrams -- Hartnett walked away from the latter, and a three-picture deal potentially worth $100 million. Directors McG and Bret Ratner were attached to flyby, with Ratner keen on Hartnett but, as the actor would later recall, "The decision was a struggle. But I just never really wanted to play Superman."

12. Ashton Kutcher
Before he tried to cast Josh Hartnett, Brett Ratner screen-tested the "Dude, Where's My Car?" star. But Kutcher eventually turned the part down, and Warner Bros' refused to give Ratner the $225 million budget he wanted. When the director dropped out of the project, it went back to its original director, McG, who once again tried to enlist Kutcher. He screen-tested again, this time alongside Keri Russell as Lois Lane. But he still thought he "looked funny" in the Superman suit and declined a second time.

13. Brendan Fraser
"The Mummy" star was up for the "Flyby" project as well, and recalled being psyched to try on the suit. He passed however, over concern that he -- like the previous Superman actors -- would suffer the "Superman Curse" and be typecast for the rest of his career.

14. David Boreanaz
The "Bones" star had to turn down "Flyby" as it conflicted with his commitment at the time to his TV series, "Angel." Years later, Boreanaz was considered for Zack Snyder's "Man of Steel" before the part went to Henry Cavill.

15. Jude Law
The English heartthrob was one of the actors Brett Ratner approached to star in "Superman: Flyby." He was also in talks to star in Wolfgang Petersen's "Batman vs. Superman," playing Clark Kent to Colin Farrell's Bruce Wayne. But Law demanded script approval over sequels, Petersen left to direct "Troy," and the project fell apart.