Relationships are tough. People are complicated puzzle pieces that rarely fit together perfectly. Differing interests, beliefs and attitudes can make an entwined life difficult. But imagine the complications if your significant other spends much of every day in a spandex costume, battling the forces of evil.

In "My Super Ex-Girlfriend," the new romantic comedy-meets-superhero flick, Matt (Luke Wilson) discovers that his needy girlfriend, Jenny (Uma Thurman) is, in fact, the super-powered G-Girl only after dumping her.

Hell hath no fury like a superwoman scorned, and G-Girl uses her vast abilities to make Matt's life a living hell. Sadly, the situation is not that atypical; in matters of the heart, after all, most costumed heroes are powerless. Consider the love life of the Dark Knight. In every Batman movie from the 1960s through today, Bruce Wayne has shown that while he might be brilliant at foiling villainy, when it comes to picking girlfriends, he's an idiot.

If you were embarking on a crime-fighting career for which you've spent most of your life training and preparing, why on Earth would you complicate things by getting involved with Vicky Vale (Kim Basinger), a snoopy photojournalist who eventually finds her way into the Batcave?

But that's just what Bruce Wayne (Michael Keaton) does in 1989's "Batman." The relationship didn't last, nor did the one with the overreaching psychoanalyst Chase Meridian (Nicole Kidman) in "Batman Forever" (1995).

In fact, Batman's so bad at choosing mates that he's fallen for the alter ego of one of his enemies, the Catwoman, twice — once in the campy 1966 TV spinoff, "Batman," and again in the dreary 1992 "Batman Returns." (And no, fanboys, it's not mitigated by the fact that he's had a love-hate relationship with Catwoman in the comics.)

Bruce, give it up. You need to stick to the casual arm-candy befitting your billionaire-playboy role. Maybe you can date Kate Moss in your next film (and leave Katie Holmes in your past, please).

It's common wisdom that one of the key tenets for a successful relationship is honesty. And yet most superheroes are reluctant to reveal their dual identities to significant others.

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Poor Peter Parker (Tobey Maguire) in "Spider-Man" (2002) and "Spider-Man 2" (2004) was never able to explain to Mary Jane Watson (Kirsten Dunst) why he couldn't be with her — not to mention why he's so unreliable and always so bruised. When she finally discovers his secret at the end of "Spider-Man 2," not only does she forgive all, but she leaves her fiancé at the altar for a shot at love with the friendly neighborhood wall crawler. Still, at the end of "2," as Spidey swings off through the concrete canyons of New York, there's a look of uncertainty on MJ's face.

"This isn't gonna be easy, is it?" she's no doubt asking herself.

No, MJ, it ain't. Just ask Betty Ross. It's understandable why Betty (Jennifer Connelly) would be more than a bit hesitant to get back together with former flame Bruce Banner (Eric Bana) in Ang Lee's article-deprived "Hulk" (2003). Boyfriends with anger management issues are never a good idea, but think about the consequences if she and Bruce ever really get into a fight. Things are bound to get smashed.

Then again, it would also likely result in some memorable make-up sex. But more on that later ....

Still, keeping the secret of your double life makes sense, at least at first. Imagine if you were a superhero and you had just started dating someone.

Would you tell them your biggest secret right away? Aside from wanting to protect them from the vengeance of your enemies, what if it didn't work out? Suddenly, your ex has information to hold over your head for the rest of your life. It's worse than confessing a foot fetish, or that you cry during DVD viewings of "The Facts of Life."

But there does come a time when a hero should come clean. One secret kept over time can snowball and lead to a mess that might be difficult to explain. One need only see "Superman Returns" right now to get a glimpse of the muck that the poor Man of Steel (Brandon Routh) is going through with Lois Lane (Kate Bosworth). It's gonna take five sequels of couples counseling to sort that one out.

Maybe, like movie stars, country musicians and goths, superheroes should stick with their own kind and only date other superheroes. Comic book stories over the years have postulated a Superman-Wonder Woman pairing (although she did have a flirtatious thing with Batman on the Justice League Unlimited cartoon). Then again, considering the fate of Elektra (Jennifer Garner) and Daredevil (Ben Affleck) in the latter's 2003 film, as well as what Phoenix (Famke Janssen) did to Cyclops (James Marsden) in this summer's "X-Men: The Last Stand," even abilities far beyond those of mortal men can't save you from a lover's super-wrath.

There's an erotic subtext to the study of superhero love, of course. While most fanboys spend time arguing about who's faster, Superman or the Flash, or if Batman could whup Wolverine's butt, other fans often engage in NC-17-caliber speculation about what a superhero love life might look (and feel and sound) like. Take the Fantastic Four. What happens if the Human Torch "flames on" in the heat of passion? Is Invisible Woman, with her super-elastic boyfriend Mr. Fantastic, the envy of women everywhere? And what about Alicia, the Thing's blind girlfriend? What's her take on her rocky fella?

In the end, it's no wonder that most superheroes remain single. After spending all day (or night, as the case may be) dodging atomic destructo-rays and nasty barbs hurled by enemies consumed by a seething desire to see them die in agony, the last thing caped crusaders need is someone nagging them to take out the garbage.

Check out everything we've got on "My Super Ex-Girlfriend."

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