Pete Davidson has finally joined Instagram — but it’s not what you think. On Monday, the Saturday Night Live star took over Calvin Klein’s Instagram to unveil his new campaign with Machine Gun Kelly. The social media surprise began with Davidson posting a casual selfie to the brand’s feed. “I got Instagram,” he captioned the post, which featured him throwing up a peace sign in a simple, white Calvin Klein T-shirt, his face mostly obscured by his camera’s flash. Explore See latest videos, charts and news The post by the famously social media averse star quickly went viral, amassing more than 400,000 likes. For his part, Kelly took to the comments section to hint that he’d somehow be involved, writing, “Are you gonna post us in our undies[?]” Hours later, the pair surprised fans by taking ov...