Levi can't quite sit up on his own yet, which is bothersome to the brothers and sister who want to play with him. So in an attempt to involve him in their construction project, they decided to build him a little chair.
I'm fairly certain that it was Abby who decided to build him a little chair, and that she coerced Caleb into giving up the blocks for his tower to help with it. And I'm also fairly certain that she managed to convince Jacob that contributing to the building of the chair was a much more worthwhile end for the blocks he had used to build his puppy. This is typically how these things go.
But however they arrived at it, it became a collaborative effort, with all elders working diligently to make certain that the younger did not fall over.
Caleb put himself in charge of structural integrity and worked to ensure that the back was connected to the sides so that his brother didn't lean back and collapse the whole thing.
Abby worked on architectural design, adding the little extras that would set this chair apart from all others. The working fans on the arms, windows built into the sides and the color choices were all her doing.
And Jacob made sure that no piece went unused, adding insect eyes and roof pieces to the outside edges, and building the back and sides as high and as thick as his siblings would allow.
I appreciated that the four of them managed to entertain themselves for so long without the whole episode devolving into chaos.