Me Two — Mary C. Ryan

OH-OH, SOMETHING'S WRONG!
Wilf needs a miracle to pull his science grade up and he thinks he's found it. OceanPups, a project that shows you how to "raise your very own tiny sea creatures," according to the ad, is bound to earn him an A. But nothing gives him a clue that experiments can sometimes go haywire...

For some crazy reason, Wilf creates an exact duplicate of himself! Losing no time in taking advantage of the situation, he sends his "twin" to school in his place, dumps his homework on him, and even sends him on a date with creepy Heather. Can Wilf get away with this outrageous hoax? Well he does until he discovers that it's he who may disappear and be replaced by Wilf Two!