Certain days of the week have special activities for specific Friends.

Tuesday: Two's Day for Pooh. All the honey values are doubled on Two's Day.
Thursday: Sandwich Day for Stitch. On Thursdays, Pudge the Fish can be found at the beach. If Stitch feeds Pudge a peanut butter sandwich, Pudge will make it sunny if it is raining; or rainy (or snowy, depending on the season) if it is sunny.
Friday: Dung Day for Simba. He gets extra dung beetles in his Bug Harvest competition against Timon on Fridays.
Saturday: "Fish Are Friends" Meeting Day for Dory. This is when the "Fish are Friends" meeting takes place in the Sunken Ship location.