I'm tired so I'll make this fast.
Pink guy used to make more simple and "innocent" music before Frank was sent to the ricefields.
Heck, in "balls in my face," he was trying to rap about helping the world. While not every song at that time had such a good message behind it, you have to admit it had a lighter tone and feel to it.
At the end of the music video which came out after Chin Chin sacrifice 2015 , we see Chin Chin still at the monoxide realm, waiting for something to happen.
After that his music got a darker and faster tone, rapping not about food for the most part, but drugs, suicidal tendicies, and murder.
Granted, this was a slow transition, but it's noticable.
And for those who are just like ehhh, Joji didn't plan it that way, he just started to make "realer" music around that time and those events have nothing to do with each other, shut up. Don't ruin everyone's fun.
So now Frank's back and we're still waiting for Pink Season. Will Pink Guy's style change back? Will he continue on his dark rode until his angry raps start affecting his personality off the music videos? Is this just Joji experimenting in a new medium of music and using Pink Guy as the character who sings it, and nothing that happens in the show will affect it? Only time will tell.