It takes a special breed of entertainer to lure a motley group of adults and children onto a stage and get them to act the part of one long Rube Goldberg-type fire pump. Lin Murphy and Tom Nicotera, two charismatic souls known collectively as the Echo Mime Company, exude a warmth and unaffected enthusiasm for their craft--clowning, white-face mime, juggling--that turns audience members into smiling, absolutely willing accomplices.

Their brief little show in the Bumper Car Pavilion at Glen Echo Park yesterday afternoon was a homey, rather makeshift affair. Presented on a bare stage, in the light of day, with only a few props and masks as theatrical aids, the performance unfolded in a series of sketches. Murphy, a beaming woman possessed of two thick golden braids, simultaneously played a devilish child and her irritable mom. She and paunchy, bearded Nicotera became courting frogs, a couple with harmonicas for mouths, a pair of robots involved in the mechanized production of humans (one good-natured spectator ultimately became their prey), and assorted other characters.

Technically speaking, they--well, let's just say Marcel Marceau needn't worry about the competition. Clarity of gesture is surely something that could stand some improvement, and perhaps the material might be developed in more sophisticated directions. Kids today are mighty precocious and visually alert--not to mention a few grown-ups.