[neatoman]

I can't find a source beyond Wikipedia but I know all of the 2012 show did air in Japan. Of course, seasons 2 through 5 aired after the show was concluded (almost right away), way after season 1 and by a different network, so it's possible that only season 1 was dubbed and the rest aired subbed.

Anyway, I think the reason the 4Kids show only got 52 episodes dubbed is because that's the minimum requirement for a syndication deal in Japan or something. Obviously that must have been a bummer for anyone who watched the back then, episode 52 ends with a cliffhanger about the looming Triceraton invasion, even if they cut that out you'd still be left with a few loose ends. Obviously episode 78 makes for a better conslusion, even if Ch'rell screaming no would be a weird final moment.

I guess that if you had to cut down seasons 1 through 3 to make for exactly 52 episodes, I'd cut these:

1. "Nano"
2. "Garbageman"
3. "The Unconvincing Turtle Titan"
4. "Notes from the Underground, Part 1"
5. "Notes from the Underground, Part 2"
6. "Notes from the Underground, Part 3"
7. "The King"
8. "Tales of Leo"
9. "Lone Raph and Cub"
10. "Reflections"
11. "The Return of Nano"
12. "Return to the Underground"
13. "Junklantis"
14. "The Golden Puck"
15. "April's Artifact"
16. "Return of the Justice Force"
17. "Touch and Go"
18. "H.A.T.E."
19. "The Lesson"
20. "The Christmas Aliens"
21. "The Darkness Within"
22. "The Entity Below"
23. "Time Travails"
24. "Reality Check"
25. "Across the Universe"
26. "Bishop's Gambit"

Now to be honest, there are only nine of these episodes that wouldn't hurt for me to remove, it's just that these 26 episodes are the least important in terms of needing to understand what's going on in case you can only watch 52 out of the 78.