The 60s series didn't show how he got them. He went into the circus without boots, then in one fight scene he's wearing them and he has them from then on.
I just checked, and you are right. What is more Dr. Tenma did several times call him 'Astro'. :huh:
BTW, the episodes ran about 27 minutes back then! Compare that with the 21:45 of any Futurama episode. I assume that most other "half-hour" programs also run for just over twenty minutes. :angry: :angry: :angry: :angry: :angry: :angry: