Theme Events happen several times per monthly and are usually weekly or one every 2 weeks. During the Event, you get the option to buy different decorations for your farms. They are normally cheaper than the normal decorations for a better happiness level, and if you complete the Event, you get rewarded with a 5x5 decoration of greater happiness. The rewarded decoration comes in four different values. The value depends on the level of your farm until you win the third level decoration (+74 Happiness). Once your win the third level decoration, place it on your farm and unlock it at the Decoration Tower, you can choose the difficulty of the Theme Event the next time it is available including a Farm Specialist difficulty that is very hard to complete. Completing the Farm Specialist difficulty earns you the highest level Event Decoration (+78 Happiness).
During the Event, you perform different required actions for like collecting fertilizer from the silo, finding ink paintings, or supplying apples. There are usually six sets of tasks to do for each Theme Event. Some sets of tasks have only one action, where as others may have up to three actions. Each set of tasks gives its own reward.