Impetuous Man is Penn Jillette

Penn does not know how his image ended up on the box. Penn talked about it a bit on his radio show. If you look closely, you can see that that the one painted finger nail Penn has is on the wrong finger nail in the illustration on the box.

Penn doesn't like the Simpsons. He and Teller were even on it once. If this happened to most any other celebrity, there would be lawsuits involved and lots of media coverage. Penn seems like he doesn't really care. I guess he finds it amusing.

Penn revealed the origin of the drawing on the final Penn Radio Show (Penn Radio - March 2, 2007 - The End.)

Unfortunately, the shows have all been removed.

Here's what Wikipedia says about it:

Penn-brand Viagra: on the February 1, 2007 show, a listener alerted Penn to a strange photo of him gracing the cover of a Chinese herbal "Viagra". The Chinese box copy claims the box contains fast acting pills that will increase a man's stamina, increase the volume of his semen, and win him respect among other men. The box depicts an illustration of a man that looks disquietingly like Penn Jillette (complete with his signature one painted fingernail) choking a woman during intercourse. The product does not identify Penn by name but seems to label him as the "impetuous man". One can purchase a bottle here for 1000 yen. It was later revealed the art work was of Penn. The artwork accompanied an interview with Penn in an American magazine. It is unknown how the art made its way to Asia.