I've had to panic pick a new costume which would be simple to make over the course of two weeks, and I've settled on this one:

http://images2.wikia.nocookie.net/__cb20091110002839/ccs/images/5/5e/Costume15.gif

The thing is I've got no idea on how to get the ears to stand up. Any time I've tried incorporating wire into something like this, it doesnt tend to work out that well, or the ends are very pokey even when bent over. It's something that has put me off doing this one for some time and I know that interfacing will only go so far before it becomes to heavy and flops.

Any suggestions at all to achieve maximum perkiness?

Put cardboard in it? Thin sheets of foam?

We got Gyarado's fins to stick up with copious amounts of padding and tension. I dunno if it will translate well though.

Maybe interface the fecking crap out of it with the stuff I used for Catnip's and mine outfits?

Putting a wire frame into it is probably best~

I know it's not the same hat, but the part which described making the ears would be the same if you were to do it, you'd just sew them onto the hood instead http://mishacosplay.deviantart.com/art/Fionna-Hat-Tutorial-265344844

I've used firm upholstry foam before and that works really well. Used it in my Mika Ito Bunny Ears. Also very comfortable to wear