Airy computer hijinks--with something of a letdown when the secret's out. Yet how could it be otherwise? Kate draws a self-portrait on her doctor-father's computer--titled (for a school assignment) "Self-Portrait of a Computer Nut"--and gets a message from an unidentified someone or something, who on next contact calls himself an extra-terrestrial, BB-9. A hoax? A mysterious admirer? Best-friend Linda's wacky ideas for eliminating suspects shame and embarrass Kate--but secret, overweight crush Willie Lomax (victim of an accidental dousing in flea dip) gets interested nonetheless. BB-9 can also be contacted on Willie's Apple; he seems to be able to read minds; maybe he is for real--and coming to earth imminently, as he says, for firsthand experience "IN EVOKING LAUGHTER." What's more real is Kate's discomfiture: she's down on Linda ("Kate, I can't help being funny"), at odds with her family ("Dr. Morrison sighed"), edgy with Willie--whose self-mocking wit makes him very likable, and hard to perturb. Then Kate and Willie meet BB-9, as arranged, in a burger joint: a quasi-kid, with a mechanical voice, who's already alienated himself by cracking weird extra-terrestrial jokes that no one gets. ("I SAID TO THE WAITRESS, WHAT WEIGHS TWO THOUSAND POUNDS, HAS FOURTEEN LEGS, THREE HEADS, AND GOES ERRRRRRRRP? . . . A CRUSTACEAN MONSTER WITH INDIGESTION.") When he also insists on telling jokes at a nearby pep rally, he's stampeded; Kate and Willie extricate him; and Kate sends him off happy by genuinely laughing at his last joke. The who's-on-the-computer? gambit, and the true-to-character humor holds up well enough to keep readers going--even if the thwarted space-comedian bombs out.