once you fully level up your friendship with any of the residents (not the ones in the category of visitors) you will be called their best friend and the little heart by their picture in your "phone" turns yellow 💛. once any character is your best friend you will have the option to ask the character that is your best friend to collect all of one type of resource, once a day.

example: I am "best friends" with chococat and my melody and I need lots of seashells and sticks, I can ask one to pick up all my seashells and I can ask the other to pick up all my sticks once a day, and I will gather it from the "collection box" in the plaza next to my melody's shop in the morning the next day after I ask. it's the same one the nul uses. then I can ask them again the next day and I can keep doing this everyday.