Lil Twist Arrested -- Justin Bieber's Sidekick BUSTED FOR DUI

10:15 AM PT Sources tell us Twist allegedly had a lit blunt in the car when officers pulled him over ... as well as some more marijuana.

Lil Twist -- Justin Bieber's lackey -- was ARRESTED for DUI in Calabasas, CA early this morning ... while behind the wheel of Justin's famous chromed- out Fisker Karma ... TMZ has learned.

Law enforcement sources tell us ... 20-year-old Twist -- real name Christopher Lynn Moore -- was pulled over for speeding around 3:30 AM on Parkway Calabasas, while en route to Bieber's mansion.

When officers approached the car, they believe Twist appeared to be under the influence of a substance ... but we're told he DID NOT appear to be drunk.

Twist was arrested and hauled to a nearby station where he was booked for DUI.