The Ralfzz are an alien race found in Marvel Comics - although they are not hostile a small group of Ralfzz caused trouble for Hulk and the world in general for a brief time.
A group of small Ralfzz children entered earth's solar system during the course of a "game." The objective of this game was to rack up point by destroying as many (uninhabited) planets, asteroids, and other stellar bodies, the child destroying the most planets would win. The Ralfzz children set their sights on a small planet, the third from the sun, and diverted a massive asteroid into a collision course with it. The destruction of earth would bring the particular kid only 10,000 points.
Doctor M.A. Forrest, an astronomer, noticed the earth-sized asteroid's change of course and contacted the military, who, in turn, contacted The Incredible Hulk, who was going under the guise of "Mr. Fixit."
The military had a new, experimental device called the "Fortified Rocket Springs", basically a set of giant leg springs used to leap long distances, The Hulk was the only one with enough strength to lift off on these springs, and be propelled into space, to divert the asteroid.
So the Hulk blasted into space, and destroyed the asteroid.
The kids were furious that someone had interfered with their game, and they went over and picked up the Hulk, who was stranded as his springs had burned up as he left the atmosphere, leading him to say, "I wish I could at last take consolation in saving the earth...but who cares?!"
As he was brought aboard, the Hulk reacted angrily, and the kids became scared and unleashed their defensive robot to tackle the Hulk, who promptly reduced the shiny robot to scrap metal.
Then the kids explained what was going on, and that they had "forgot" to check if earth was inhabited.
With everything neatly wrapped up, the Ralfzz kids returned Hulk home, as he noted that they reminded him of himself.