The Lorax didn't really know how it happened, it just did. The rips in time, and space. He had no idea why the once-lers showed up. Of corse he wasn't talking about his own greedy beanpole, but the other three who had appeared over the corse of a few months. they didn't seam too keen on leaving either. The Lorax had gotten used to referring to the group as a whole Once-ler. The individuals were, just that, individuals, with their own nicknames, and personalities. His own Once-ler had taken to the appropriate name of Greed-ler, and the others were similar to that. A definition of themselves.
The first one to show up was about the age of Greed-ler. He dressed similar, and the borax would have thought they were clones, if it weren't for the fact that the Greedier had green eyes, and slightly pointed teeth. The other once-ler was much nicer though. He wasn't as money hungry, instead having the charisma that seamed to have won off of Greed. They called him Gent-ler, because of his gentleman like nature.
The next one to show up was much younger then the other two. Like the Once-ler who had made the Lorax the promise not to cut down any more trees. The young Once-ler was horrified at the deforestation, and had a pretty fair rant at Greed, without any fear in his eyes of the powerful businessman. They called this one Oncie, because he was the original Once-ler. The one they all were at one point.
The last one was a monster. He had been discovered after some of the lumberjacks went missing. This one was older then the others, but defiantly not able to care for himself. The creature (for there was no way he was a man at that point) was hiding in a cave when they found him, living off the flesh of the dead lumberjacks. He was covered in blood, and had fiercely sharp teeth, and vicious claws. He looked like he'd turned both biological weapons on himself a few times, as well as other people. They called him Red-ler, because of his blood lust, and crimson eyes.
The four were some times more trouble then they were worth, but sense the others came things began to change for the better in the forest. Oncie was their resident environmentalist, constantly coming up with ways to make thneeds without chopping down all the trees, wile Red helped with an element of fear. Greed need only look at the psychotic madman to know what would happen to him if he didn't change how he ran things. Gent had taken over the media, and customer service aspects of the once-ler, as he was the most charismatic of the group. Red didn't really do anything, except strike the fear of God into Greed, and give them something to worry about other then thneeds.
No the Lorax didn't know how, or why it happened, but he sure wasn't complaining.
A.N. Just the basics of this universe.