"Doug's Big Catch" is the first part of the ninth episode of season one of Nickelodeon's Doug.
The episode begins with Doug and Porkchop on a boat with Mr. Dink in the middle of the ocean in a stormy weather. A gigantic fish is seen hooked on to the reel on the end of Mr. Dink's fishing pool and swims away, dragging the boat with it.
The episode is back on the scene and later fast forwards to the scene that shows Doug in Mr. Dink's house, where the latter explains Old Chester, a fish who lives in Lucky Duck Lake that stole his wallet as a kid 30 years ago. He shows Doug a picture of the fish he drew on a sheet of paper and says that he would load his boat with every technology he could bring. Doug then realizes the zeal this trip would go into.
Doug's imagination: On the submarine SS Dink, Mr. Dink tells Doug, the captain of the submarine, that there is something coming their way via tracking device. Doug then informs Mr. Dink and Skeeter that they are going head to head with Old Chester.
Mr. Dink convinces Doug to tag along to catch the fish. At Lucky Duck Lake, where the Big Time Bass-Off is about to begin, Doug and Porkchop grab some lunch for Mr. Dink and run into Roger and his gang, who mock Mr. Dink for attempting to catch Old Chester and wonder what sucker would tag along with him to catch it. Knowing the embarrassment he would suffer for collaborating with Mr. Dink to catch Old Chester, Doug and Porkchop inconspicuously sneak back to Mr. Dink in the boat and tries to convince him to let him sit this quest out, but to no avail. Mr. Dink, realizing that everyone had been secretly mocking him behind his back, decides to refute everyone. Doug then gets a guilty conscience of what he is about to decide.
Doug's imagination: Mr. Dink, now old and lonely, is sitting in his boat still fishing in the middle of the lake little more than morose over the fact that he hasn't caught Chester.
Realizing that he had to stand by Mr. Dink, Doug quickly reconsiders and goes with Mr. Dink to hunt for Chester. The other boats take off as the fishing competition starts. But due to Mr. Dink's boat being overloaded, it instantly sinks and Mr. Dink's plan to catch Chester is quickly revoked. Mr. Dink relinquishes his quest to catch Chester and admits his defeat. So Doug makes a fishing pole of his own to catch Chester. But Mr. Dink reminds Doug that it is futile to catch a fish on the dock since there are no more fish there. But Doug doesn't give up and he and Porkchop try anyway. He later gets a powerful grip and struggles to reel the fish in.
Doug's imagination: A news reporter is inside a bathroom delineating Chester, who is almost bigger than the whole bathtub. He interviews Doug, who gives out a succinct reply of his success "Great!" Mr. Dink is also next to him and is little more than gloomy.
As Doug continues to pull the fish in, he wonders if he should let Mr. Dink catch Chester so he doesn't feel like a failure. So he asks him to assist him, which he does. Mr. Dink yanks the fishing pole and successfully catches Chester in the hand. Doug becomes confused when he learns that Chester is smaller than he imagined. Mr. Dink later has qualms of catching the fish and discovers that he loves him. So he tosses the fish back into the lake. Porkchop then discovers that Chester has dropped Mr. Dink's wallet on the dock, much to Mr. Dink's delight. However, he later becomes infuriated when he discovers that the fish had stolen his money when he peeks into the wallet to check for any cash.
Doug is back in his room writing in his journal and discovers that his own wallet is missing. He sees Porkchop, dressed as Chester, carrying it and chases him around the room playfully.
- The Big Time Bass-Off contest is later referenced to in an episode of Jim Jenkins' second series, PB&J Otter.