"California Dreaming" may have turned up a young actor qualified to impersonate Alfred E. Neuman in the recently announced "Mad" movie project. The highly specialized oddness of Dennis Christopher is the only potential contribution to the sum of human amusement discernible in this vacuous impression of the Southern California surfing culture.

If surfers are the louts they appear to be in "California Dreaming," they don't justify dramatic treatment. If their number includes personalities or aspirations worth observing, this movie overlooked them.

"California Dreaming" never locates a story among its shreds of subplots, and the tone fluctuates arbitrarily from gross caricature to facetious lewdness, not a particularly elevated range.

Christopher is supposed to be odd-twerp-out in this setting. Some sort of juvenile exile from the Midwest, he arrives on the beach trying to ingratiate himself with gauche slang and a gaucher personality. He attaches himself to a former beach Tarzan, played by Seymour Cassel, who now runs a bar. He gets a crush on Cassel's daughter, a beach nymph embodied by Glynnis O'Connor, who correctly dismisses him until called on to change her mind and find him a cute sex partner for no compelling reason.

Christopher's ingenuous wimpiness surpasses anything ever seen. Unlike Charles Martin Smith in "American Graffiti," Christopher doesn't endear himself to the audience. This specimen, drolly nicknamed T.T., is the buggy, prissv kind of male ingenue who makes you cringe.

Altough he blunders around like Jerry Lewis in one of his errand-boy roles, Christopher is not a comic star. He can't sustain the show on gaucherie. He's simply distinctive enough, and probably capable engough, to be humorously exploited in the appropriate context. Robby Benson should encourage him, because Christopher may be the only young actor around who can makes Benson appear down-right potent in comparison.

The movie's flickers of pictorial interest derive from foolproof subjects: surfing sequences and unclad or barely clad actresses. When it comes to taking care of anything resembling dramatic business, the filmmakers are always out to lunch.

Tanya Roberts, a striking oval-faced brunette with lustrous blue eyes, attracts the camera in a special way, but her role as the abused girl friend of a cloddish surfer is too minimal to reveal much about her acting ability. CAPTION: Picture, Glynnis O'Connor and Dennis Christopher in "California Dreaming"