Okay, well... your goal here is to get 'a ton of signatures from people who agree with your statement or position'*, in this case, about an Animorphs anime. How are you gonna find these people? Well, I think your best chance at an audience who'd agree with you would in fact be online. Here and other Animorphs sites, sci-fi sites, book-lovers sites, etc. Facebook. Facebook, Facebook, Facebook. And if you really want to go at this, find school book fairs, or used book stores, and try and spread the word there. But if you have your petition online, that means that you'd be able to have a much broader range than *just* the book store you visit or wherever. I'd suggest putting something up on each of these sites, and maybe more if you find others:
www.ipetition.comwww.change.orgwww.gopetition.comwww.petitiononline.comwww.petitionspot.comAnd yes, it would have to go through Scholastic, Inc. for final approval, considering they do own the rights to Animorphs. It would be kind and considerate to ask Applegate, but legally, it's not required.
*pretty much the definition of a petition