Coloring books are where most kids start to develop their artistic dexterity. They are available relatively cheap, they are often related to cartoon characters or objects familiar to very young children. They provide guidelines for children who are learning to control their hand movements by "coloring inside the lines".
The alternative is to buy coloring books in a shop or order the physical coloring book online. If you order the physical book online, it can take ages to receive it. Then you have to wait for the item to be delivered. If you buy a coloring product in digital form, you receive it within minutes of purchase. Normally, once your payment is made, an email is instantly sent to you and includes your purchase.
When you are planning to hold a Sponge-Bob birthday party, try to send the invitations around 2-3 weeks ahead of the party date. Order matching invitations or make your own. Cut a starfish or pineapple shapes from card stock paper.