Okay - I'll confess. This is the movie that made me love what Michael Keaton could do. He does a beautiful parody of someone doing a parody of James Cagney, with charm to spare.
The supporting cast are solid workers all, and will step right up and do a fine job in this '80s comedy. A spoof of the '30s-'40s gangster movies, it breaks new ground constantly, with remarkably original material. (Well, yeah - some of it has been copied since - but when this movie was made, it was original, and much of it has _not_ been copied elsewhere.) Watch Joe Piscopo warn people to not do ______, with one of the great taglines of spoofs. Watch Roman Moronie do things with English profanity that would make your spinster grammar teacher laugh. Watch amazing sight gags, such as pet-store owner Johnny Kelly using the price-tag gun on his puppies and dusting his kittens. Watch the greatest "warning against sex" educational film ever made. Watch the most amazing misrepresentation of church Latin done, while a guy who never took shop class assembles a Thompson machine gun from parts. Watch lines you'll be using in casual conversation for the next decade. Watch Maureen Stapleton do the perfect antithesis to the hard-working mom, with surprise gags that you'll never see coming.
If you see a gag that doesn't hit your funny bone, be patient - another will come along in 30 seconds or less, and the odds are, you'll need to pause until you're done rolling on the floor several times. Duckies and Bunnies? Them, too. Watch for the subtle stuff - some of the sight gags can go by unnoticed the first few viewings.
There are a few minor flaws - but it's probably the best of the spoofs. Some come close, but none of them are quite this good.