Here's a synopsis from fan Charles Garofalo:
"I believe this story introduces Mr. Pompous, as Astroboy's neighbor, rather than teacher like in the manga. A time machine crashlands in Pompous's backyard, nearly wrecking his house and alerting Astroboy. A teenager named Teddy Tyme comes out, he's from the 23rd Century, and he's going back to the past to get his father, who's been gone too long. Astroboy and the excitable Mr. Pompous go with him. Ted's dad has gone way into the past trying to get specimens for a zoo he's building, Astroboy and company have to contend with a tribe of tailed cavemen aggravated over the kidnapping of one of their members by Dr. Tyme and then, even farther in the past, some dinosaurs. When Tyme is nearly killed by a rampaging dino, he gives up on his zoo idea and reforms. Back in the 21st Century the crabby Mr. Pompous nearly has a fit when he sees an unflattering cave painting that very closely rsembles himself..."
Thanks very much for that detailed listing, Charles!