A physical assessment of Astro is that he’s a fully grown (huge) Great Dane, though Elroy insists he’s “just a little puppy”. He can more or less talk, but like Scooby Doo, modified with an R at the beginning of each word, rendering it from English to Barking. Both dogs were incidentally voiced by actor Don Messick, but apart from the speech impediment sound pretty different.
Astro is not smart. He knows standard doggy commands but not which is which. He shakes hands for ‘play dead” or something like that, but is enthusiastic and overwhelmingly doggy affectionate. He smothers George with affection sitting on the sofa with his arm around him, like they’re on a date, a consequence of being the same height.
Astro is not very brave; he detains a burglar in the house when he passes out on him in terror. Astro is another family obligation on George, not a crime deterrent.