Norby and the Court Jester & Norby and the Terrified Taxi

This tenth volume of the complete children's sci-fi series features a time-travelling space odyssey and a spring break vacation gone terribly wrong.
Norby and the Court Jester
On spring break from the Space Academy, Jeff Wells and his robot, Norby, head to the planet Izz for a toy and game fair. They look forward to seeing Princess Rinda and her little robot, Pera. But when Norby receives a telepathic message from Pera-part of which is "help!"-Norby and Jeff are sure that trouble awaits. And whatever's going on, it's most likely thanks to the evil Ing, the new Court Jester on the planet Izz.
Norby and the Terrified Taxi In an adventure that changes the course of Earth's history, Jeff Wells and his robot, Norby, are catapulted through time and space to find a dangerous and bad-mannered prankster, Garc the Great. In their search for Garc, Jeff, Norby, and their colleagues are trapped by a powerful alien Connector Ring. Now all they have to do is escape, find Garc, save the human race, and return to Earth in the correct time frame!