Oakland rappers Digital Underground, one of the most-talked-about rap breakthroughs of last year, celebrate the absurd. Ringleader Shock G is hip-hop's split personality: He has an alter ego, Humpty Hump, who wears a big plastic nose and started a dance craze with the group's smash single ''The Humpty Dance.'' In ''Packet Man,'' remixed here from the first album, we are reintroduced to a pusher who deals in ''sex packets,'' an orgasm-inducing hallucinogen, as an alternative to more harmful substances or more risky sex. Digital Underground released this EP to tide fans over until the group's next full-length album and to revisit the magic of their platinum-selling debut, Sex Packets. But don't be fooled: This is not a cheap knockoff to capitalize on their success. Like all of their best tracks, ''Same Song,'' their current single, transcends being a musical track for a party to become the party itself. Over a sparse, throbbing bass line, Digital's three rappers (they sound like four: Shock G double-tracks himself to play Humpty) tag-team to testify about champagne-drenched, chicken-eating limo rides, safe sex, and their refusal to let their music be diluted for pop success. Elsewhere in this collection, unfortunately, the groove loses its structure and lags more than it struts. But as an appetizer for their old fans or a primer for new ones, This Is an E.P. Release will not disappoint.