There are a few Jigglypuff in Route 3.
Yes it evolves when you use a moonstone on it.
Clefairy, Jigglypuff, Nidorina, Nidorino
could be in mt moon but under the Pokemon center next to mt moon. go down and you will see grass then go left, up then theres a pile of grass there and its there. will take a while to find sometimes because of nidorans and spearows. Route 3 is the only place you can find Jigglypuff in FireRed. Even there it is uncommon.
You can't catch it on Firered you can only catch it in Emerald
Clefary is in mount moon, and jigglypuff is right outside. If you're patient, check out the safari zone, but you could also get some as prises at the rocket casino.(Scyther, dratini, porygon, ect.)
route 3or4
Catch a Jigglypuff and a Ditto or catch both male and female Jigglypuff and bring them to the fourth island in the Sevii archipelago. You'll find a day-care center there. Of course, you'll need to complete the Elite four challenge before getting there.
You can catch a Jigglypuff in the Safari Zone Meadow area.
Breed Jigglypuff/Wigglytuff
You can breed jigglypuff or wigglytuff to get it.
around pewter city
Yes it evolves when you use a moonstone on it.
Use a moon stone on it.
Yes.
You can find it on Route 3, about 10% of the time.
Jigglypuff evolves into Wigglytuff with the use of a Moon Stone.
Clefairy, Jigglypuff, Nidorina, Nidorino