<p>There’s a song in the musical “Water for Elephants,” now playing at the Nederlander Theatre on a national tour, titled “The Lion Has Got No Teeth.” The song describes the deceptions of the circus and how the circusgoers — whom they cynically call “rubes” — are fooled into thinking the onstage feats are more impressive than they are.</p><p>It’s a dangerous thought to put in the heads of an audience. A traveling show about a traveling circus runs the risk of having its talk of showbiz and artifice backfire.</p><p>“Water for Elephants” follows Jacob Jankowski (Zachary Keller), a veterinary student who leaves school after the death of his parents. Jacob hops a train, which happens to carry the Benzini Brothers circus.