Yonkou #3 has been all but told outright by omae no kaasan that his avatar came from his website, but YK3 hasn't picked up on it despite having that avatar for such a long time. One of the convos they had was like,
OnK: Hey Yonkou #3! That's a really awesome avatar, where did you get it?
YK3: It's a really cool avatar do you like it too. :)
OnK: Yeah! It's a really awesome avatar. I'm sure the guy who created it spent only a few minutes digging up the manga page and several hours in photoshop to spruce it up. It's certainly not worth taking off his site, I'm sure even the most elementary artist could do better.
YK3: I really like it though, it's a cool avi.
I still can't believe he doesn't know, even after all that.