Odds are if you remember Bobcat Goldthwait, you remember him as weirdo-gangleader-turned-rookie-cop Zed in the Police Academy movies and from a bunch of stand-up comedy specials back in the ’90s. While his name may not have been a topic of conversation lately, the guy’s been quietly working away in Hollywood, doing tons of voice work, directing a couple hundred episodes of “Jimmy Kimmel Live!” and creating a pair of edgy cult films (1991’s immortal Shakes the Clown and 2006’s taboo-busting Sleeping Dogs Lie). Now comes Goldthwait’s latest writing/directing effort, the gloriously offensive, scabrously funny, surprisingly subtle black comedy World’s Greatest Dad.