Dennis sneaks out on his sitter to go to the movies where his parents are and causes trouble at the theater.

After a truck knocks over a street sign, Dennis and Tommy set it back up--incorrectly. As a result, Mr. Wilson gets a hole dug in his backyard for the swimming pool that was intended for the other address.

Henry and Mr. Wilson have a fishing trip planned and are trying to keep Dennis from finding out. Dennis however knows something is up when he sees a package delivered to the house that has fishing stuff in it and so it turns out to be a long night for Dennis as he won't rest until he finds out what's in the package. Eventually he figures it out and so Henry and Mr. Wilson end up taking Dennis along after all.

Dennis introduces his visiting grandpa to town spinster Miss Cathcart, who takes an interest in him, sings for him, and pretty much makes him miserable.

Mr. Wilson gets a telescope and is convinced he spotted a missing satellite in space. What he actually spotted was a ping-pong ball that glows in the dark from Dennis' pop gun that Dennis was shooting in the air to win a contest from a kids TV show called Captain Blast.

Henry and Mr. Wilson decide to plant Dennis a flower garden of his own hoping to keep Dennis out of Mr. Wilson's flower garden, but what Dennis does is take the bulbs out of Mr. Wilson's garden and replace them with sweet potatoes and when Mr. Wilson sees the bulbs at Dennis' house he thinks they are Dennis' and he sticks them in Dennis' garden, but, Dennis and Mr. Wilson both win a blue ribbon though.

Dennis tries to help Mr. Wilson's old neighbor sell his house by using his drum. Mr. Wilson, however, has different ideas, so he tries to talk a retired couple with no children into moving in next door, which almost works until Dennis and his friends come bursting into Mr. Wilson's house. So, what happens is the window repair man is moving in next door, and he has 4 kids, which is not what Mr. Wilson wanted at all.

Mr. Wilson comes back from vacation with a changed attitude, more free spirited and cheerful. However, that all changes when Dennis and Tommy camp out in the back yard because a friend of Henry and Alice have a record with wild animal sounds on it such as lions and have speakers in the patio turned up so Dennis and Tommy can pretend they are out in the jungle. Mr. Wilson hears the sounds of the animal roars and thinks that the wild animals are after the boys so he runs outside without his glasses on and carries his sword.

Dennis thinks that his dad is in money trouble so he starts out selling bottles and before you know it everyone in town thinks that the Mitchell's really are in trouble with money.

The Mitchell's start a rumor that they are moving to New York in order to keep Mr. Wilson in town to receive a plaque. However, things start getting a little out of hand once Dennis gets word of it as the whole neighborhood thinks the Mitchell's really are moving to New York.

It's Christmas time and Dennis is going around the house looking for his presents. Henry and Alice think they have the perfect place to hide them, The Wilson's house in Mr. Wilson's closet which works for a while but eventually Dennis figures it out when he goes over to the Wilson's house and Mr. and Mrs. Wilson are over at his so Dennis opens the closet door and sees his gifts.

Dennis gets to be in a play put on by Mrs. Webster that his favorite TV star Whip Crawford is in only Whip doesn't want to be in the play because he claims his feet hurt so he tries to dodge Mrs. Webster and everyone else. So, Dennis who doesn't give up does everything he can to get Whip Crawford in the play including going to his hotel room and talking to Whip Crawford himself which in the end works.

Dennis, Tommy, and Stewart start a clubhouse in Mr. Wilson's crawl-space. After a fortuneteller tells Mr. Wilson that he will hear from one of his late relatives, he hears noises in the house and thinks a late relative has come back from the dead, but it's Dennis and his friends in the basement.

Dennis has a tree house that hangs over Mr. Wilson's back yard. Mr. Wilson is not thrilled about it because he thinks that Dennis up in the tree house will scare all the birds away. He tries to teach Dennis about bird watching, which in the end turns out good, when Dennis takes care of a sick bird and helps Mr. Wilson get an award from the state bird society.

Mr. Wilson pays $250.00 for a rare gold coin from a con artist that turns out to be a fake coin. The good news is that the coin gives Mr. Wilson a free wish when Dennis throws the coin in the fountain in the park, Mr. Wilson wishes that Dennis would go on vacation for a week and his wish comes true in the end when he learns that Dennis is going to his Grandpa's for a week.

Dennis wants a bike so bad that he will do almost anything to get one such as taking one away from another child, Trying to win one in a bean contest, riding Mr. Wilson's exercise bike. Finally in the end Henry takes Dennis shopping for a bike.

The Mitchell's are having a open house party to entertain one of Henry's clients but people are having trouble finding the house, that is until Dennis finds an open house sign and puts in in the yard and soon the house is over run with people who think that the open house sign indicates the house is for sale.

Mr. Wilson is plagued by a full-grown duck that Dennis adopted when its original owner moved away. At first Dennis hides the duck from his parents, but when Mr. Wilson complains about the damage caused to his garden and himself, Dennis reluctantly admits to having the duck. His father helps Dennis build an enclosure for the duck, but Mr. Wilson continues to have problems with Dennis' new pet -- and begins to scheme how to get rid of it even if Dennis and his parents won't.

Dennis wants to put up a swing in his yard and ends up chasing a cat who Mr. Wilson is house sitting for a friend up a tree in the process. Meanwhile Henry tries to take Alice out for their anniversary which Henry completely forgot about. the ice cream man tries to get the cat out of the tree and ends up with his ice cream truck shut off so the ice cream man puts all of his ice cream in the Mitchell's ice box.

Dennis takes care of a dog named Charlie who inadvertently wins a prize for a painting that Mr. Wilson painted after his tail brushed the painting.

After Dennis meets Mr. Wilson's sister Helen and she reads the book "Treasure Island" to him and his friends Dennis decides he wants to be a pirate and dig for buried treasure, So, Mr. Wilson draws a map of his yard for Dennis and his friends to find so they can dig for where Mr. Wilson wants to plant his flowers. When Dennis and the other boys start digging they find a treasure only it came off a costume bracelet of Alice's that Henry put there for the boys to find. But, when Mr. Wilson sees it he starts getting excited until he finds out that it isn't real treasure.

When Dennis is over at one of his friends he notices that his friend has his own TV set so Dennis is doing anything he can to convince his parents to buy him a TV set of his own, However when Henry and Alice both turn him down he has Mr. Wilson show him how to work his remote control which was a mistake cause then Dennis rents a remote of his own and ends up controlling Mr. Wilson's TV set from the guest room with the remote that he rented.

Dennis wants his dad to be a hero so bad after Johnny Brady's dad always seems to get his picture in the paper for some heroic act. So Dennis tries to talk to the town reporter to put Henry's picture in the paper and make him a hero.

Dennis and a bunch of other town boys are collecting papers for a charity and the prize for the boy who collects the most papers is a Silver dollar that's worth $600. When Mr. Wilson gets word of that he is determined to make sure that Dennis wins the prize so that he can get the silver dollar.

To help the bees find honey Dennis sprays a fragrant smell on Mr. Wilson's camellias, Mr. Wilson of course gets carried away thinking he has developed a rare flower that will make him a fortune only to discover that the fragrant smell is from the Dennis spaying perfume on his flowers.

While Henry is out of town Dennis wants his mom to have a nice birthday with lots of presents. Mr. Wilson sends him down to Finch's drug store to shop for his mom. When he goes down to Finch's drug store he ends up causing chaos down there with Mr. Finch and to make matters worse he puts a sign on him advertising people to get his mom lots of birthday presents.

Dennis and a boy that Mr. Wilson was responsible for are left without a babysitter after agreeing to let one sitter sit for the boys cause Mr. Wilson and Henry both end up canceling theirs.

Mr. Wilson has a yard full of starlings that he desperately wants to get rid of so he hires a professional named Mr. Prince to do the job that has a record that will get rid of them. However, thanks to Dennis the record brakes so when Miss Cathcart starts singing the starlings start to fly away and to finish them off Dennis puts liver in Mr. Wilson's tree which eventually brings tons of cats.

New neighbors, the Driscolls, share a party telephone line with the Mitchells, which causes problems for both families.

After Dennis hears that the city is going to tear down Mr. Dorfman, the postman's bench Dennis, Tommy, Margaret and Stewart try to build him a new one but Dennis gets sick and has to stay in the house and watch the other 3 try to build the bench.

After Joey has to go home Dennis has no one to play with Henry is going golfing, Mr. Wilson is going bowling, Alice has a date to play bridge and his other friends aren't around So, Dennis decides he wants to go visit his Grandfather which is far away so when he asks Alice to take him to his Grandfather's and she can't Dennis decides to start walking there but, he doesn't get far as he ends up getting stopped by the police.

Dennis and Tommy's efforts to sell Valentine's Day cards in July cause problems for Miss Cathcart, Mr. Dorfman, Mr. Wilson, and even Mr. Carlson the gardener. There's also a run on Valentine's Day cards in July. Mr. Wilson buys the rest of Dennis' cards, hoping to avoid more trouble, but he ends up in trouble with the police.