Mars Attacks was a popular line of bubblegum trading cards released by Topps in 1962. Following on the heels of their successful Civil War News card series, which had featured plenty of blood-and-guts, the new Mars Attacks series took the violence one step further into the science-fictional realm; hapless Earthlings were crushed, burned with rays, roasted alive, frozen to death, etc. Naturally, kids loved all of it; and just as naturally, parents hated it.
Mars Attacks was reputedly the brainchild of Topps employee Len Brown, who took some science fiction comic book art and pasted it onto a trading card to show his boss Woody Gelman, who seemed to think that a card series devoted to the subject was a good idea. Brown wrote the text of the cards; the art was pencilled by Bob Powell and then turned into finished paintings by Norm Saunders. Disguising themselves as 'Bubbles Inc.' (to protect their clean-cut, all-American image in the minds of parents), Topps had planned on releasing the cards as Attack From Space (and some test items were even created); but wisely, the decision was made to tighten up the name.
Unfortunately, the afore-mentioned parental reaction caused the cards to stay on the market for only a short time. The product had had only a limited distribution anyway; but after receiving bad press, the cards seemed to disappear from store shelves forever. These factors, coupled with the fact that so many mothers threw away their sons' collections, has meant that the Mars Attacks series is difficult and expensive to complete.
Since then, the cards have been remembered fondly by collectors. Eventually, an additional series of cards was created to 'finish' the story; a small line of comic books was launched; and of course in 1996 Tim Burton directed the big-budget, star-filled, comically violent Mars Attacks! movie.
You can see the entire Mars Attacks card set here.