Superman went through significant changes during the "Silver Age" of comic book publishing (the late 1950's thru early 1970's). Most of these changes involved publishing stunts to make more interesting writing for the character and his friends.

Most notably were the introduction of variations of the "super" theme. For a time, there was a super-dog (Krypto), super-baby (Superbaby), not to mention a super-ape, super-horse, and even a super-something-or-other (Proty, a shape-changing glob that hung out with the League of Super-Pets in the 31st century). Yes, the League of Super-Pets, too!

Also were variations on the 'kryptonite' concept. There were the following variations (other than Green-K, which just poisoned and eventually killed anything Kryptonian--especially Superman):

  • Blue Kryptonite: the opposite of green, only affected Bizarro-Supermen (made them stronger)

  • Red Kryptonite: unpredictable, never the same effects twice--made Superman into a giant ant, made him into twin duplicates of himself, etc.

  • White Kryptonite: killed any form of plant life

  • Gold Kryptonite: Could permanently take away a Kryptonian's super-powers (such as General Zod and his fellow cohorts)

  • Jewel Kryptonite: reinforced the psychic/telekinetic powers of Kryptonians incarcerated in The Phantom Zone

  • Purple Kryptonite: (only seen once) Could temporarily give normal humans Kryptonian-like powers (turned Lois Lane into a "Superwoman" for a day)