Zack is happy to test a new android his father helped develop for Nebulonics before she goes into production, but her ability to learn causes problems when she develops a crush on Zack after watching a romantic movie.

When summer arrives on Nebulon, Zack discovers that his best friend, Drake, is afraid to learn to swim and decides to teach him before they go on a trip to water-covered planet Araxie.

Zack and Drake venture to Gluco, the candy planet, for some Easter fun but while competing in such activities as an egg toss and a three-legged race, Zack is so determined to come in first that he considers cheating to win.

"Zack is headed back to Earth for the first time since moving to Nebulon. He can't wait to see Bert and show his new friend, the former bully Seth Stevens, all around his old stomping grounds. When Zach's dog Luna escapes and goes missing, sightseeing plans take an unexpected turn. Will Zack find Luna before he has to head home to Nebulon?--

Zack is shocked to find a large, green, six-eyed creature sitting in his place at school one morning, but soon learns that he and the "monster" have a lot in common.

Will troublesome cabin mates ruin Zack's summer at space camp on the planet Sylvan?