One in a while a Web application comes along that's so damn useful, even we'd invest in it. Facebook? Meh. MakeMeBabies, the site that lets you create ruddy-cheeked mashups from any two photos? Its diapers will be filled with nothing but spun gold. Here's what the site came up with from photos of Facebook CEO Mark Zuckerberg and girlfriend Priscilla Chan. After the jump, we give a few other notable couples the same treatment. Please do add your own in the comments with our image-upload feature &