I'm going through all the endings for my first time, all in "order" (based on how the wikis order them) and just reached the ending right before you get the Hero Badge from little Tata.

So, okay, I know that some of the endings are joke-y in nature, but so far I haven't gotten to one that's this....inexplicably non sequitur. Not saying that's a bad thing, but the other ones (even the Kilwala, Nu, and the frog one) can sort of be explained in a meta context as to why the devs put them there. Beating the game with just Crono and Marle before the story even starts? Bam, you get the development room ending. Cool. Beat the game, having only witnessed the cathedral/Frog meetup portion of the story. Bam, you get an ending where he...for some reason, hooks up with Leene. 'Kay. The "good night" ending, I feel, is just there to tell you "Okay, you found out about Lavos, instantly defeated him through way of Mr. bucket, and totally said 'fuck all' to any and all future party members, eras, and plotlines. Here's Spekkio(?), a Nu, and a random frog just messing around. Enjoy!"

But this one? Okay, so we can assume Frog is just chilling in his underground house, Masamune-less, leaving Tata to hold on to the hero badge. He wants to live up to the hype, and so maybe he mixed some Power and Magic Tabs into his Guardi'o cereal and that's how he beat the mooks at Magus' castle! Either way, he gets there, and...

...what? Crono, Marle, and Lucca? What?? (And that's not even covering the beginning portion which is just Robo Atropos recreating the game's intro)

So, what's your interpretation? Joke ending or not, I like trying to find some reason as to why the devs put each ending where it is, which is why answers like "don't look too much into it" don't cut it for me. Why are our heroes now evil? What's the connection between the first scene with Robo, and the 600AD scenes? And how did Tata go from a scared little kid and into the next Dragon Quest MC??