Bart and Milhouse attend a Spinal Tap concert, which degenerates into a riot. Nonetheless, Bart is impressed by the band and wants to become a rock guitarist. Homer and Marge decide to buy Bart his own electric guitar, but he finds it impossible to play as he is not musically gifted like Lisa(when she tries to play a duet with her sax). The next morning on the school bus, Bart tells Otto he thinks his guitar is broken, but Otto wows his passengers with an impromptu concert. The performance meant that they are now late for school, so Otto is forced to drive recklessly to get there in time. The bus causes numerous incidents before turning over onto its side in the town square, where it also smashes into the statue of Jebediah Springfield.
When Officer Lou asks for Otto's driver's license, Otto is forced to admit he does not have a license (nor is he wearing his own underwear on which he wrote his name as proof of his identity). He is suspended without pay, and Principal Skinner takes over his route. However, Skinner finds driving the bus hard going, being a less aggressive driver than Otto, and ends up being trapped at a busy intersection for an entire day. Otto, meanwhile, goes to the Springfield Department of Motor Vehicles but he fails the driver's test that is administered by Marge's sister Patty partly due to his poor driving ability and partly due to the fact he asks Patty if she was born male. He is also unable to find a new job, and therefore cannot pay his rent and is evicted from his apartment. Bart finds him living in a Trash Co. Waste Disposal Unit, and agrees to let him live in the Simpsons' garage. Homer and Marge disapprove of this but reluctantly agree to let him stay.
Otto quickly makes a nuisance of himself. Homer begins to lose patience with Otto and demands that he be sent on his way. Marge and Bart encourage him to give the driving test one last try. Otto goes to the DMV to take the test again, angry that Homer called him a "sponge". Patty refuses to let him take the test after a comment he made about her being born a man. However, when Otto tells her that he wants to pass so he can prove Homer wrong and "staple his licence to Homer Simpson's Big Bald Head", she relents out of spite for her brother-in-law. Otto performs even worse in his second test, but Patty grants Otto his license anyway after he entertains her with stories of Homer's crude behavior. Now a properly licensed driver (albeit under probationary status), Otto regains his job and Skinner is happy to return to his normal job as Principal.
In this episode, Otto's driver's license is shown onscreen after he passes the driver's test. Otto's license reveals him to be 5 ft 10 in, 150 lb, his hair and eyes are black, and he was born on January 18, 1963. His driver's license ID number is VOUS98213.