Bats, sharks, moth, or dino villagers.
These other two feel pretty even to me, so I'll list both:
1.
Brewster wants to expand his cafe to help Tom attract more tourists, so Brewster asks if you like Ice cream. You say absolutely! Brewster tells you if you can raise the funds, Tom will upgrade the cafe and ice cream can be served. After the upgrade, Brewster puts you to work each day making 4 orders of ice cream. Orders can be for any resident villager (highest percentage), any NPC currently on your island(mid percentage), a villager who has never been on your island (very low percentage) who may provide dialog for you to invite them to the campsite. If invited, they will show in the campsite the next day.
The trade off is that those served will be in the cafe chowing on ice cream for the rest of the day. Plan your day wisely.
Declining to work for Brewster when you walk in for the first time that day will lower your friendship with Brewster, and he may say he is out of everything when you ask for something to drink. If you still insist, he'll say well, I have some old left over coffee grounds I can use. He will give you that and you will be smiling with a disgusted face at the same time.
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2.
When 30 days have past from helping Harvey achieve his dream of a campground on his island, Harvey gives you a call asking you to come meet him. You go and he tells you that he wants to expand and get more visitors to his island. He wants you to get the raw building materials to give to Cyrus to build an arcade.
The arcade will have 3 playable mini games.
An endless runner type, An endless shooter type, and pinball.
You will have to buy tokens from Harvey to play the games but don't fret, you can get tickets from based on scores you achieve in the games. Tickets can be used for neat items you can't get anywhere else. Be prepared, they will cost an insane amount of tickets.
After trading tickets in for a prize for the first time, Harvey will tell you about how he would like to be outside again once more. You suggest to him to hire someone to run the arcade for him so he can go back outside. He agrees and a new NPC will be in the arcade the next day. A few more special prize options will be added when the new NPC arrives but the new items will cost even more tickets.
Harvey will then ask for your help raising funds to set up a multiplayer mini game field behind the arcade. You have the chance to earn a few more tickets than normal but the games will be a tad harder. You can play with friends or with your villagers that live on your island (computer controlled) or both! This will have 3 games, soccer, volleyball, and tennis. 6 total participants. Jocks will be a tad faster.
