Not illegal where? If you're in Japan here's a fun thing to try:

1. Ask ChatGPT to generate some Ghibli-likes for you.

2. Find a local photo printing store prepared to print and blockmount them for you (this is actually the hardest part - most will politely tell you to piss off).

3. List them on Mercari or Rakuma.

4. Regularly relist them as they're periodically removed for violating local counterfeiting laws.

5. Eventually explain yourself to a judge and maybe go to prison for a year.

Technically you only need to do 1 and some of 2 to be committing a crime in Japan.