Lincoln needs to prove he is mature so he can sit at the adult table.
One evening, Lincoln is annoyed by the messy and annoying antics of his younger sisters at the "kiddie table", and he envies his older sisters, who get to eat with Mom and Dad at the "grownup table". Some time later, he gets Clyde to come over to help him prove that he is mature. After following Clyde's lessons on talking 'adult", learning the individual table utensils, and looking sharp, Lincoln manages to get his parents' approval to get a seat at the grownup table.
However, the experience of being mature proves to be not as exciting as Lincoln had hoped; there's no singing or joke-telling, the family engages in boring small talk, and liver is served rather than chicken nuggets. That night, Lincoln has a nightmare in which he is bound to the grownup table. Upon waking up, Lincoln realizes that it's his fault for wanting to be so mature and devises a plan to get back to the kiddie table.
The next evening, he arrives at the grownup table and makes a complete fool of himself by imitating his younger sisters' unsavory and crazy table manners. When his parents have enough of his behavior and ask him if he wants to go back to the kiddie table, Lincoln happily obliges and joins an in-progress food fight to celebrate Lincoln's return. As he happily engages in the mess, Lynn asks if she can join them. Lincoln agrees and Lynn says she never thought it would be possible to leave the grown up table. The other older sisters join their younger siblings as well, and the 11 children start a big food fight, as the episode ends.