It literally only took Professor Utonium sugar, spice, and everything nice (plus an accidental dose of chemical X) to preform human transmuation, so I dunno why Ed Elric’s child prodigy ass couldn’t do it.
Now that I think about it they’re not actually human, and the Professor wasn’t trying to bring anyone back. The Powerpuff Girls are homunculi and this is the hill i die on. Chemical X was liquefied philosopher’s stone.
Look at these images from the comics
There’s not one for Bubbles though because she’s sinless