See the Movie, Buy the Pajamas?

THIS summer's movie season has two battlefields: the box office and the toy store. Several thousand products linked to ''Pocahontas,'' ''Batman Forever,'' ''Casper,'' and ''Mighty Morphin Power Rangers: The Movie'' are starting to flood retail outlets, making for a hard-fought movie merchandise campaigns.

''It's the most competitive I can recall in a long time,'' says Linda Berkeley, whose MCA Merchandising Group handles ''Casper'' products.

Most of the movie-related merchandise predictably is geared to young children: ''Pocahontas'' action figures, ''Casper'' pajamas, ''Batman'' T-shirts. But some summer action films aimed at older consumers -- from ''Congo'' to Kevin Costner's $175 million ''Waterworld'' -- will be accompanied by merchandise, too. An interactive CD-ROM version of ''Johnny Mnemonic'' supplements the film's release, for example.

Even though most people predict Disney's ''Pocahontas'' will rule at both theaters and cash registers, MCA says ''Casper'' will compete with more than 1,000 ''Casper'' products. Problem: The title character, a ghost, is mostly invisible. One solution: glow-in-the-dark ''Casper'' bed sheets.