The folks at Marvel know that it's never too late to take a chance to tweak their distinguished competitors at fancy Southern California comic publisher DC. Back in April 2013, DC ran a month of covers under the 'WTF Certified' banner, with 'shocking' twist reveals on fold-out covers. The F in WTF is of course a naughty word, which made some retailers uncomfortable, and DC shuffled its feet and said it would not put the ribald WTF branding on its actual covers.
A whole two years later in April 2015, Marvel has decided to remind the world of DC's embarrassed walk-back with What The Duck month, featuring twenty comics with variant Howard the Duck-themed covers inspired by iconic images. In the PR, Marvel boasts that the covers will be 'WTD Certified', so this is not a simple coincidence. This is mock-making in the classic Marvel manner.