Two readable, eye-able, distinctly playable playlets--albeit slightly coy and mannered in both conception and picture-book presentation (by comparison, for instance, with the old Judith Martin/Remy Charlip Tree Angel or Jumping Beans). They do, however, put story-book conventions--and childhood delights--to clever dramatic purpose. In ""The Mysterious Stranger,"" a Princess, locked in a tower by a Witch, is rescued by a Mouse--who nibbles ""at the foot of the tower"" (i.e., the feet of three children, in turreted sandwich boards, standing on stools) which, from the tickling collapses in a fit of giggles. Only then does the Mysterious Stranger (in sunglasses) reveal himself to be a prince in disguise--too late to rescue the Princess. (""Oh well, next time . . . maybe."") ""The Magic Spell""--about a girl and her little brother, turned into a cat--is somewhat less arch, and more roundly involving. First, there's the girl's explanatory dialogue with (again) the stranger, as the brother plays pussycat; next, the play-within-a-play of his enchantment (a sort of reverse Little Red Riding Hood); then, the unspelling of the witch's spell (""Saskatchewan and Kalamazoo/Kankakee and Timbuktu . . ."") by the little girl who confesses ""Spelling is my worst subject."" So, naturally, she needs some help from the audience and, as time runs short, from the stranger . . . until little brother reappears and (another dispensable tee-hee) big sister bemoans the loss of the cat. The first play is laid out in comic-book form; in the second, the play-within-a-play is a cartoon sequence; both feature flat, stylized figures in hot oranges and pinks. Included, too, are some performance pointers ""For Adults Only."" Amusing and adaptable.