1. Puck (the transforming robot) - he started out reckless and just wanting to help, but he really kicked butt once his dad completed him. It would've been great to see Puck grow up and be a really helpful robot with his awesome transforming ability.
2. Pepe (the merman robot) - for someone who is supposed to look over and protect the golden reef, he sure depended on Astro fending off the sharks. As a robot, I would've loved to have seen Pepe with some abilities and kick some butt.
3. True (the liar robot) - I know he died but he deserved redemption. you could tell he was only lying coz it was in his programming and that he wasn't doing it deliberately. What doesn't make sense is why the professor didn't just disable the lying unit after True told the girl the lie.
4. All "Greatest Robot In The World" robots - this 2-parter is one of most favorite stories of the series. I think it would've been cooler to have been introduced each of these "greatest robots" individually in earlier episodes so that when they died at the hands of Bruton it would've been much more powerful and tragic (not that there wasn't enough death and tragedy in the whole series
