There's not a lot to do for the 4th week in the event. I finished without any trouble. There was a space of time where I had to wait for the last task to pop up though. To find event items, filter Show All by Special--Event Rewards in Buy Mode.
The cake is a Birthday Cake. Most options are for sims to age up, so be aware of that! You can choose to light candles for a birthday and to celebrate. You can eat the cake, but I don't think you can after the cake is used to hide in. (?)
Your sims has an option to hide in the cake and jump out in whatever outfit you choose for them.
Then they dance while others celebrate.
The dance is the old Smustle.
Once the cake was used, I only saw options to celebrate or clean up.
Love it! Thank you for sharing those photos! ❤️
