Doug's Derby Dilemma is the first part of the sixth episode of season two of Nickelodeon's Doug.
The kids are all building soapbox racers for the Mt. St. Buster Downhill Speed Race, and they all want to win the secret mystery prize, and Doug and Skeeter are having trouble keeping their racer a secret. But during the race, there's a disaster on the track, and everyone finds out that helping a friend is more important than winning.
The episode starts with a snake seen in the road. He later moves out of the way when a gang of cars zoom through the road. During the race, Doug introduces himself and Skeeter in a French accent. With their newly built go-kart, they zoom past the other racers and attempt to cross the finish line.
The others read about the 1st annual Mt. Saint Buster Downhill Rally through a sign on the window and a mystery prize for the winner of the rally. The mayor announces to everyone that the 3rd-place winner gets a trophy of him, the 2nd-place winner gets a similar trophy that is slightly bigger, and the 1st place winner gets a prize that is an enigma to all of the others.
They sign up for the race and Doug and Skeeter work together in Doug's garage to build a go-kart for the imminent race. After they finish, they dream of what the mysterious prize is. Later, Roger shows up to take a view of their newly-built go-kart, telling them that Beebe and Chalky's go-kart looks the same as theirs. But Doug and Skeeter don't believe it a bit and as Roger leaves, they take a second thought and run to Beebe's house, leaving Roger to sneak inside Doug's garage.
When Doug, Porkchop, and Skeeter make it in front of Beebe's house, they spy on them to realize that Beebe and Chalky's go-kart looks nothing like theirs. They are eventually caught by the security guard and Doug tries to convince Beebe that he and Skeeter were making sure that she and Chalky didn't steal their design. When Chalky accuses them for trying to take his and Beebe's design, Skeeter retorts that his and Doug's design is a winner. Beebe then says that she wants double security and nobody sees her go-kart until the day of the race as Doug, Porkchop, and Skeeter are about to be tossed out by the security guard.
The three friends return to the garage, only to discover that Roger had tricked them and demolished their go-kart while they were away. So with Mr. Dink's help, the two friends go inside his tool shed and build an even better go-kart, one that no one sees until the day of the race, with Mr. Dink's new security system to thwart any intruders or spies. After they finish as the weeks elapse, Patti then knocks on the door and Doug, using Mr. Dink's video camera, opens the front door to let her inside the shed so she could borrow a ball peen hammer. But Patti ends up going through the side door of the shed. Doug and Skeeter try to hide their new go-kart from her and give her the ball peen hammer right before she leaves.
The next day, the race begins and Roger attempts to run Doug and Skeeter off the road.
Doug's imagination: Roger is racing against Doug and Skeeter ancient style, and instead of go-karts, they have racing chariots. Roger's wheel slams into Doug and Skeeter's wheel as they continue racing.
Roger continues to attempt to run Doug and Skeeter's go-kart off the road, only to have the front of his go-kart busted when Doug and Skeeter's go-kart rams into it as they continue racing. Doug and Skeeter are now in second place and attempt to past Beebe and Chalky. While inside Beebe's go-kart, Chalky accidentally presses the airbag button, thinking it was the radio button. He and Beebe start to suffocate and Doug and Skeeter stop to help them out of their go-kart just in time. The airbag completely inflates and Beebe's and Chalky's go-kart floats away (apparently, the airbag actually filled with helium). Roger ends up winning the race and gets the mystery grand prize, which is a full week as vice mayor of Bluffington. To his annoyance, he has to mail a number of letters for everyone in Bluffington.
Back in Doug's room, Doug is writing his latest event in his journal and explains that he had to help his friends, as he feels that there are more important things than winning a downhill race. When Doug reads an ad for the annual Bluffington Dog Sled Race, he encourages Porkchop to enter the race, prompting Porkchop to run away after discovering that the prize is a trip to the North Pole.