Rapper Who Can't Rhyme

Listen up, buttercup. This one's about wordplay. See, a rapper is supposed to rhyme. But if they can't, it's like they have a "speech impediment," which is also what you'd call someone who can't talk right. It's funny 'cause it's unexpected and kinda makes fun of the rapper. You probably didn't get it, but that's okay. You're clearly not the sharpest tool in the shed.