Heroes who have a physical limitation to their powers — say, aquatic heroes who require regular immersion in water to survive — will always have a built-in time limit of at least one hour. This time limit will be absolute; if the hero is more than one minute late, it will always be assumed that he/she will instantly die.
Cosmic rays, gamma rays, radiation: it’s all the same wonderful stuff, able to work wonders on the genetic code and produce a million types of super-powers without any long-term ill effects.
Mutants always receive some special power from their genetic uniqueness. Female mutants never receive any disfiguring side effects with their mutant gifts.
Corollary: This rule may be modified to allow heroic mutants with freakish appearances, provided they display sufficient angst and ponder on a regular basis why they protect the humans who fear them.
Magical heroes can weave their spells only by chanting and waving their hands. Gagging them and tying them up will render them powerless, forcing them to note the irony of having so much power at their command and yet unable to use it.
In any instance where a hero’s power comes from a scientist’s super-secret serum or device, a tragedy involving both the scientist’s death and the destruction of said serum or device will occur immediately after the hero receives his/her powers, thus ensuring the hero is the only one to benefit from the treatment.
Corollary: All power-producing serums and gadgets are created by lone scientists who never bother to write down their notes or formulas, making doubly sure no one can re-create their work after they die.
Heroes and villains with superior knife-throwing skills will be uncannily accurate with any sharp edge, just as characters who are expert marksmen can pick up any projectile weapon and fire them with pinpoint accuracy.
Whenever a hero/villain possesses the power to create gold or precious metals out of thin air, there will always be a reason why the hero does not use that power for his/her own personal gain.
Heroes with the ability to generate immense amount of heat from their bodies never have to worry about scorching the ground with their feet, or causing heat-related injuries to their teammates who stand near them — because everyone knows heat never transfers through the air!
Superfast heroes never have to worry about the effects of running very fast: costumes burned off from heat friction, sonic booms shattering windows, shoes disintegrating under the pressure, dust particles hitting their faces at the speed of bullets, etc.
As every hero knows, all it takes to go forward or backward in time is to run or fly really, really fast. This is also the recommended method for piercing the dimensional barrier.
Heroes of American Indian origin will always have some sort of mystical connection to the spirits, and their superhero identity will be intimately based on their Amerindian culture.
Heroes of Asian descent are always masters of the martial arts.
Super-fast heroes are never quite fast enough to actually do things at the speed they seem to have. For example, they cannot read up on a subject in just a minute. They aren’t fast enough to outrace the weapon of the villain. Even if they can exceed light speed, they’re not fast enough to find the villain and defeat him before he can blink an eye. They’re just fast enough to be really fast, but not so fast as to actually do things really fast.
Heroes that transform due to a physical transfiguration (e.g., Captain Marvel, Firestorm, etc.) never have any effect on their surroundings. Captain Marvel could be buried at the center of the Earth, and “Shazam” would still call that magic lightning bolt.
Characters that can shrink, grow, or make multiple copies of themselves need not worry about the laws of physics. Their clothes change with them, and no one wonders where the extra mass goes or comes from when they make the change.
Characters with the ability to manipulate a specific natural force or form of energy can do anything they want as long as they claim they are using the force or energy they control. This includes, but is not limited to, using gravity to teleport, using magnetism to brainwash people, or using electricity to fly.
Heroes composed of or capable of turning into an inorganic substance will be flexible and able to move even if the substance is normally rigid (like stone, wood, or metal). If the substance is normally “soft” (sand, clay, or water), they will be able to form their hands into hammers that can shatter concrete without any noticeable difference in their hands’ mass.
A mutant’s innate genetic structure is capable of understanding abstract human-imposed concepts like “weather” (which, while naturally occurring, is really a catchall term for several unrelated physical phenomena), “language” or “machines.”
Heroes who shoot some form of energy from their hands never have to explain where the source of said energy is, nor do they have to explain how the energy can blow holes in walls and then merely knock a person unconscious just seconds later.
No hero is ever depicted in less than prime, Schwarzeneggarian physical condition… unless his powers rely on him being fat, in which case he’s morbidly obese. (Note: The “he” is intentional. There are no fat female heroes.)
All heroes are handsome. If a hero is less than handsome, then he must be designated the team’s token “character,” with regularly scheduled soliloquies about his cursed state. (Note: The “he” is intentional. There are no unattractive female heroes.)
There are no flat-chested female superheroes. An athletic woman who has trained herself to perfection and has the bulging muscles to prove it will always have basketball-sized breasts that do not get in the way when the hero runs, flies, does backflips, etc.
All female heroes who make the jungle their home will never display anything less than flawless manicures, make-up and hairstyles at all times.
Corollary: Same goes for Stone Age women whom heroes might meet during their time-traveling adventures.
All female heroes have shaved armpits and legs. Stretch marks, birthmarks, or skin blemishes caused by fate or acts of violence are never visible.
All African-Americans appearing in stories printed before 1985 will sport a hefty Afro hairstyle.
Baldness = badness, certain wheelchair-bound mentors excepted.
Goatees = evil, certain archers excepted.