Mojo Nixon has the rough personal presence of a friendly but not-quite-housebroken German shepherd--he means well but tends to make a mess, and he'll bite your leg if angered. His musical shtick is to take half-remembered (or -received) roots-rock moves and set 'em to key components of his personal etiological analysis of society, which has in the past produced such gems as "We Gotta Have More Soul!" "Debbie Gibson Is Pregnant With My Two-Headed Love Child" and "She's Vibrator Dependent." Nixon is not, of course, as dumb as he acts--I think he once believed that there mere weightier concerns in the world, but then decided that no, there weren't--but he thinks it's fun to keep us guessing, and only gives it away on occasional masterpieces, notably a career-justifying assault on "This Land Is Your Land" a couple of years back. Anyway, having split with his longtime Sancho Panza, Skid Roper, he's now leading a rock band filled out with a bunch of LA scene demi-stars (John Doe, Country Dick Montana). His new record, Otis, is what you'd expect--standard issue Mojo, including the rockin', very funny "Don Henley Must Die" and the reggaefied "Perry Mason of Love" ("You, you look sweet / As Della, Della Street"). Memphis ringleader Jim Dickinson produced, or rather didn't. The show, with the Cavedogs and Dead Milkmen on the bill might strike some as overkill--standard warnings to the faint of heart, the easily offended, the subtle. Saturday, 7:30 PM, Riviera Night Club, 4746 N. Racine; 769-6300.