Post Malone and Jackass star Steve-O have a history of tattooing each other, but for Steve-O’s 50th birthday, the musician gave the stuntman a NSFW tattoo he’ll have a hard time forgetting, and apparently that’s on purpose. For this special occasion, Posty drew a big penis and balls over Steve-O’s right eyebrow with a pair of “drops” just to the side of his eye. Why Steve-O Got a Penis Facial TattooIn sharing the tattooing through TMZ, Steve-O revealed there was a very specific reason for agreeing to the tattoo. “Let me tell you why I got it,” says Steve-O. “It’s to see how long before I’d tap…