THE HOTTEST item at the beach so far this year isn't a leash for an invisible dog or those bouncing deely-boppers but a ticket for Ocean City's first world movie premiere, Violets Are Blue, a love story starring Sissy Spacek, Kevin Kline and Bonnie Bedelia.

Last Saturday, the resort's Chamber of Commerce put more than 1,300 tickets on sale for $40 apiece. By Monday afternoon, only 75 seats remained for the April 13 debut.

The Chamber's Anne FauntLeRoy credits the box office rush to the town's 1,600 extras, who were paid $40 per day for their work in the film, which was shot in Ocean City during the summer and fall of 1984.

The $8 million Columbia picture was conceived and produced by Baltimore-bred Marykay Powell, who spent many childhood summer days strolling along the Ocean City boardwalk.

Kline plays Maryland Coast Dispatch newspaper editor Henry R. Squires, who rekindles a 15-year-old relationship with Gussie Sawyer, an internationally known photojournalist played by Spacek. Their affair is renewed after they bump into each other while covering a controversial condominium project on Assateague Island.

The story begins in the late '60s, and the scenes for that period were shot in the older, southern end of town, some 50 blocks from the skyscraping condo corridor built along Ocean Highway during the '70s. The movie includes scenes supposedly of Belfast, Ireland, which were shot in the streets of Baltimore.

Spacek and her husband, Jack Fiske, the film's director, who live on a farm outside Charlottesville, are expected to be joined by Bedelia, Powell and others at the premiere. A buffet at the Carousel Hotel is included in the ticket price; proceeds will benefit local charities.

"Canada's 10 Best Films, A Festival of Canadian Films" continues Friday at the American Film Institute with Richard Farnsworth's moving portrayal of Canadian train robber Bill Miner in the 1982 production The Grey Fox. The 92-minute film is double-billed with Don Owen's penetrating Nobody Waved Goodbye. The program, sponsored by the Embassy of Canada, begins at 8:30.

La Vraie Nature de Bernadette screens Sunday at 9 p.m., and Les Bons Debarras on Thursday at 9. Both films are in French with English subtitles. The Canadian series will continue through April 11. For a complete schedule of screenings and showtimes, call 785-4601.

Village Voice dance critic Deborah Jowitt will lead this Sunday's edition of the ongoing "Footroots" dance and film series at the AFI. In "Images of the American Frontier," she'll focus on Martha Graham's interest in American folk dances, including clips from her 1958 dance film Appalachian Spring. Other dance clips will come from Elmer Gantry and Marjoe. For more information, call 737-1662 or the AFI box office, 785-4601.

If you really loved Michael J. Fox in Back to the Future, MCA Home Video figures you'll probably love owning the film as well. The Universal City, California-based video packager thinks the 116-minute Robert Zemeckis- Bob Gale screenplay has a great future on videocassette and will begin retailing the film for $79.95 on May 22.

SHORT TAKES -- In Heaven There Is No Beer?, a lighthearted look at America's polka subculture, screens free at noon Friday at the National Archives, Eighth and Pennsylvania Avenue NW. On Thursday evening at 7, see Bound For Glory, Hal Ashby's Academy Award-winning portrait of American folk hero Woody Guthrie played by David Carradine. The 148-minute movie is also free. Call 523- 3099 for information.

The nine-part Saul Landau film series at the Institute for Policy Studies winds up this Sunday at 7 with his 1982 Quest for Power. Cost is $2. The screening is at 1901 Q Street NW. Call 234-9382 weekdays.

The Northern Virginia Community College's French Film series this Sunday offers Pauline at the Beach (1983), starring Arielle Dombasle and Amanda Langlet as her teenage cousin. The 94-minute screening is free and begins at 7:30 at the Reston Community Center Theater, 2310 Colts Necks Road, Reston. Call 467-4500 or 450-2571 for reservations.

On Monday, the Smithsonian Resident Associates' retrospective on Orson Welles offers his 1962 The Trail, starring Anthony Perkins and Jeanne Moreau. It screens at 8 in the American History Museum's Carmichael Auditorium. Cost is $4.50 for members; $6 for non-members. The Resident Associates' "Contemporary Spanish Cinema" series continues Tuesday evening at 7:30 in Carmichael Auditorium with El Cochecito. The 1960 winner of the International Critics Prize in Venice, it was banned in Spain by Franco. Cost is $5 for members; $6.50 non-members. Call 357-3030.

The Sky's the Limit, the history of ballooning, plus a reenactment of the first flight and shots of other balloon journeys, will screen free on Tuesday at noon in the National Geographic Society's Gilbert H. Grosvenor Auditorium, 1600 M Street NW. Call 857-7133 for information.

Ginger Rogers stars in the 1944 Paramount production of Lady in the Dark on Wednesday at noon in Carmichael Auditorium. It's part of the free "America on Film" series at American History.

On Thursday at 11, 12:15 and 1:30, the Renwick Gallery will offer free screenings of the Washington-produced The Stone Carvers, winner of an Academy Award in 1985.