When a Connecticut housewife bought a videocassette for her children at a local mall last month, she thought she was getting Buttons, Rusty and the Easter Bunny. When the kids popped the tape in the VCR, however, out came the X-rated San Francisco Girls before the cartoon ever showed. The press had a field day wondering how such a thing could happen. Those in the business know the mystery is why it doesn't happen more often.
''Every conceivable mistake associated with labeling has happened,'' says one video duplicator. Dupers regularly track tapes and check individual copies to guard against mistakes. But given the odds when they copy different films onto thousands of cassettes at once, all it takes is one cassette thrown into the wrong batch to get a boo-boo like Buttons. (Another run-of-the-mill goof produces neatly packaged blank tapes.)
Plainly, the Buttons tape wasn't blank before it was duped, though no other X-rated versions have been reported. Ten years ago, Walt Disney unwittingly distributed porn, when copies of one video contained a fragment from a porn film. Don't worry, though, about leaving the kids alone with The Little Mermaid: Disney's duplicator now limits itself to new tape or what the industry calls ''virgin'' stock. And maybe that's the real lesson all kiddie- film distributors should learn.