Episode 7. Yuusuke offering Jou's butt to distract a dinosaur.
Yuusuke: Hey, this guy's butt is tasty!
Jou: Don't make it remember things like that!
Episode 31. Yes, this has arguably the saddest moment in the show, but ignoring that one part, the episode is actually pretty funny. However, the ending is the best part, where Yuusuke's usual moral-delivery backfires on him.
Junichi: Vega Baby, although I am a boy, I learned the meaning of maternal love. Now I know the same feeling that a mother has.
Yuusuke: The feeling of wanting to protect its mother...could be compared to the Liveman trying to protect the Earth.
Megumi: Everyone should give it a try, just like Junichi.
In one episode, it would seem that Mazenda has gotten ahold of a 'dirty secret' of Yuusuke. He then proceeded to fight tooth and nail to make sure that secret never came out to public, but Mazenda did that anyway. That secret? It's just about Yuusuke once sent a love letter to Mazenda back when she was still Rui... and got flat out rejected. (For her part, Mazenda reacts with an oddly bland "oh yeah, that was a thing that happened".)