You know, I only said it was like a drug, and has more to do with the way the voice actors (technically actresses) read their lines than anything else. Perhaps they were exaggerating for effect...
It does say something about the character of the group of seven, though. Littlefoot, Chomper, and Petrie had no interest in relaxing in the mud, while Spike and Ruby did. Cera was initially reluctant, but ended up enjoying it a lot, and Ducky said that it would be nice but ultimately didn't want to disappoint her friends. Petrie did not like the mud because of what it would do to his wings, Littlefoot seems to active and virtuous to lie around for long, and Chomper is probably too energetic to sit around in mud for a while.
It is worth noting that Ruby, Cera, and Spike went back to the mud pools in a later episode (the one with Hip, Nod, and Mutt), but this was simply a plot device to prevent there from being a nearly unmanageable 10 protagonist characters in an episode.
