Calvin throws his books, saying he hates school assignments. He says he has to make a leaf collection. Hobbes asks how many leaves he needs. Fifty, Calvin replies. Hands in pockets, Calvin says that just when he thought of a loophole, Miss Wormwood said each leaf had to be a different kind. Hobbes says she has his number.

Hobbes asks when Calvin's leaf collection is due. Calvin tells him two weeks. Hobbes says that's only three or four leaves a day. Calvin says he's not working weekends. Hobbes says then it's five leaves a day. Calvin says his weekdays are booked until next Thursday at 6 PM. Hobbes says he'll need fifty leaves an hour. Calvin says it's impossible.

Hobbes sees a leaf for Calvin's collection. He doesn't want it. It's a beautiful afternoon, and he won't waste it doing busywork for school. Hobbes tells him it would be one less leaf to collect later. Calvin replies it's one leaf more than he needs right now. As Hobbes tosses the leaf, he says somehow, it's always right now until it's too late.

Susie asks if Calvin has started his leaf collection. Calvin says he's been visualizing the conception process. Susie is almost done. She says it's almost like a treasure hunt. Calvin yells to her that it's a stupid, boring, forced assignment. It isn't fun. Susie says that when life gives you a lemon, make lemonade. Calvin says when life gives you a lemon, wing it right back and add some lemons of your own.

Calvin asks how Susie could almost be done if the collections aren't due for a week. Susie makes it a game. She sees how many leaves she can find each day. Then it's not an assignment, it's fun. Calvin asks if she knows that's one of the ten warning signs of hopeless dweebism. Angrily, Susie walks off. She says she bets another sign is moving to the next grade each year.

Riding down the hill in the wagon, Calvin tells Hobbes that the teacher reminded the class there is only a week left for their leaf collections. They should be half done now. Hobbes reminds Calvin he hasn't started. Calvin says he works better under pressure. Hobbes clarifies that he only works under pressure. Calvin says the work time is more miserable, but there's less of it.

Calvin asks Mom if they can go to the arboretum, since he has to collect leaves for the school project. Mom says they can go that weekend. Calvin thinks it would be better if they did it sooner. Mom asks when it's due. Calvin says the notebook is in the car and the park closes in twenty minutes. Mom says she's making dinner.

Calvin is grabbing leaves off the ground. He can't believe Mom wouldn't take him to the park. He says it's no wonder he gets bad grades. Hobbes says he did spring it on Mom at the last second. Calvin complains that's when he thought of it. The problem is that Mom isn't flexible. Calvin wishes there was some way out of the assignment. Suddenly, a spacecraft appears above them.

Two aliens come out of their spacecraft and ask to see the supreme earthling potentate. Calvin says they're speaking to him. One of the aliens says he chose the landing site. Kudos to navigator Nebular.

The aliens are taking over the world. Calvin asks why. The aliens reply earth is prime real estate. Calvin says he never thought of that. One alien says there is charm, atmosphere, and a quiet galaxy. Hobbes says the atmosphere needs cleaning. The other alien says it's a good fixer upper.

Calvin says he can't let them come in and take over the planet. The aliens tell him to prepare for war. Calvin offers to trade the earth for fifty alien tree leaves. One alien whispers the primitive fools must use leaves for currency. It's a deal. Calvin says he needs them by 8:00 tonight, properly identified and labeled. The aliens race off, saying their leader will be most pleased.

Hobbes asks Calvin if he's trading earth for fifty alien tree leaves. Calvin says he'll have the coolest project in class. Plus, he doesn't have to waste any more time on gathering his own leaves. They can goof off all day. Hobbes says then the aliens take over the earth. Calvin replies it isn't like the grownups have done such a bang-up job.

Mom tells Calvin he can't watch TV until his leaf collection is done. He says it's getting done as they speak. Mom asks what he means. She wants to see the collection. Calvin says she should sit down. Upstairs, Calvin grumpily walks in saying Mom didn't even want to hear about it.

As they play, Hobbes says it's almost bedtime, and the aliens haven't returned with the leaves. Calvin says it's a long trip. Hobbes asks what happens if they don't show up. Calvin says they told him they would. Hobbes wonders if they got lost. Calvin tells him their superior technology prevents them getting lost. Hobbes says it's a big universe. Calvin offers to turn on more lights.

Calvin says the aliens haven't shown up. He bets the aliens got back to their planet and procrastinated. He bets they have no respect for deadlines. He bets they put it off and are doing a lousy job at the last second. Hobbes rolls his eyes and wonders how anyone could be so irresponsible. Calvin says if they aren't there in five minutes, he's not handing over the earth.

Hobbes sees headlights over the trees. Calvin thinks it's the aliens. He goes to collect his leaves. Dad sees Calvin outside collecting leaves in his pajamas. Dad has a flashlight. He tells Calvin to get in bed. Calvin says space aliens left the leaves for him.

Susie asks Calvin if he was up late doing the leaf collection. Calvin tells her his leaves are from another planet. Susie looks at them and says he took fifty maple leaves and cut them into weird shapes. Calvin informs Susie that aliens now own the earth and he told them girls make good zoo exhibits.

Calvin says the teacher didn't believe his leaves were from an alien planet. She told Calvin it was obvious he did it last night and make a mockery of the assignment. Calvin grabs some leaves and tells Hobbes the teacher won't admit it was a pointless project. He asks who cares about leaves. He calls it useless knowledge. Hobbes tells Calvin he's holding poison sumac. Calvin asks what makes Hobbes say that.