If you use fantasia, can you ever switch back?

before I use it, I just want to make sure if there's a way to cancel it to bring back your old characters looks?

I haven't tried it yet, but I assume another fantasia could be used the same way. And they are talking about making more available somehow.

I, too, would like to know this. As a Galka in XI, sometimes I get urges to switch to Roeg.

I think my curiousity would be satisfied if I'd just run into a Roeg in SCH AF because I want to see how awesome/silly it looks.

Also, is there a way to get more Fantasia? Or is it a one-time thing only.

Once you accept your changes, there's no way to undo them. You can cancel in the middle of making changes and be returned to normal, but it will always have the option of changing your features when you log in. There's no way to get more Fantasia right now.

A single fantasia potion lets you change your appearance one time, and that is the end of the story. No free take-backs. If you want to change your appearance again, you need another fantasia.

They're going to have an optional service (read: paid service) to get more Fantasia eventually, but it won't be here for 2.1.

You only get one phial of fantasia. If you use it and do not like your changes, you may petition S-E customer support and tell them that you have made a mistake. They will investigate the use of it and if deemed appropriate, may return your phial of fantasia. You will not however have your appearance reset. You can use the returned phial to return your character to its original appearance or a new one.

This request can only be done once, so make sure you get your second appearance right. There are plans to eventually sell it, but there is no clear date. It is unlikely to be included in december's patch 2.1 though.

Some players actually gained two Fantasias though - players of the original version of FFXIV (1.0) were sent a second Fantasia on account of some 1.0 players accidentally skipping the 'one time only' character modification we were given when our original characters were transferred into ARR. This was a 'spur-of-the-moment' thing though and was not advertised - I only found out about it when I received it in Moogle Mail.

So yeah, 1.0 players can get up to two Fantasias, but sadly everyone else only gets one.