“The Wild Thornberrys Movie” is perfectly watchable and occasionally--mostly when the neurotic monkey Darwin is on screen--even clever. But it traffics in stereotypes--notably Eliza's stuffy British father and his obnoxious parents--and never rises to inspired heights within either its animation or storyline. The voice actors are okay and the songs, by the likes of Paul Simon and Peter Gabriel, are not memorable. On the basis of this film, it's difficult to fathom the Thornberrys' appeal. Voiced by Rupert Everett, Marisa Tomei and Lynn Redgrave. Directed by Jeff McGrath and Cathy Malkasian. Written by Kate Boutilier. Produced by Arlene Klasky and Gabor Csupo. A Paramount release. Animated. Rated PG for some adventure peril. Running time: 86 min. Opens 12/20.