The king puts on his trousers just like everyone else, one leg at a time!"" And with that discovery (made innocently by Bud, the Royal Window Washer), King Ivor's ""vain, egotistical manner and mean, despotic ways"" turn the formerly-toadying populace into a howling mob. King Ivor tries vainly to get into his trousers some other, two-legs-at-a-time way (by swimming, swinging, being juggled, catapulted, jousted . . .); but to no avail. Then, just when the mob is screaming for his head, he has an idea; and to the fury of Slammo McJock, the rowdy ""Royal Pretender,"" and his cohorts, King Ivor appears not in trousers but in ""royal robes."" ""And that,"" sneaky R. Kraus concludes, ""is why kings wear royal robes."" Fast, furious and funny--thanks also to vigorous full-color drawings (painterly caricatures, really) by Fred Gwynne.