Do Pilates make your butt appear bigger?

NO! If you have a small toosh, or a medium size one you'll just tone it up. With any exercise, if you work out a certain area over, and over you'll build some muscle or get more muscles. the buttock are muscle overall so if you're looking to getting it bigger, work it. Just don't expect a big difference.:)

Not pilates . There are some exercises as rollerskating or iceskating that are likely to increase the muscles of the glutes. There are also specific sets of weight resistance exercises for that purpose.