Maybe I'm being hyper-critical, because this was after all a kiddie show, but there's one thing that's always bothered me about "Round and Round" -- that nobody, including all the doctors who examine Underdog, even suspects that the charm he's wearing around his neck could be the problem.
Maybe they thought, since the alien seemed so friendly, that the necklace was harmless. What I found so confusing and contrary, though, was the episode with the Excalibur swords: After helping with a train wreck, Underdog complains about a pain in this back whenever he bends over. When it's learned that one of the swords is missing, Underdog reaches into his cape and pulls the missing sword from his back. Now, considering that he has been shot, hit on the head with sledgehammers, had safes dropped on him, and walked away unscathed from explosions, how is it that a sword pressing into his back would harm Underdog?
"I'm in such bad shape, I'm wearing prescription underwear." Phyllis Diller 1917-2012
Interesting that you should mention the episode with the Excalibur swords because I thought the two episodes were kind of redundant of each other.
I have noticed that TV series back in those days were not terribly concerned with internal consistency. That even applied to dramas. There's a first-season STAR TREK TOS episode that speaks of Spock's parents in the past tense as if they;re dead, but then they show up in a second-season episode.
These days, series television seems much more concerned with internal consistency.
Old post, but:
I don't recall this episode, however, if the Excalibur swords were supposed to be based on Excalibur, it could simply be that they are viewed as enchanted; able to penetrate what no other weapon can. Vulnerability to magic is a common weakness of ultra-powerful heroes; Superman suffers from it.