Is it possible to have animal who moved out mover back into your town?

Its imposibble to having they back (For execption for Rolf)they will leave your town forever, in Animal Crossing: Wild World, if tu befriend a villager, they will give tu picture of themselves so tu won't forget they forever, the picture are rare and can't be found anywhere else.
NOte: Rolf will mover to your town if tu talk to many times if tu visit your friend town with Wiiconnect24/DS wierless communication o WFC, if he wants leave your friend town, talk to him in many times, he will sometimes mover back to your town, hope I helped :)

It's possible in New Leaf, if 16 other villagers mover out first. Not sure about the other games, though...