In the album liner notes, Adam Duritz explains:
Somewhere Under Wonderland was almost entirely written in the Fall of 2013 with the help of Millard, Dan, and Immer in The Garden at my house in Greenwich Village, NYC, although tidbits, ideas, etc… were recorded off the top of my head in the back of the bus, walking down the street, while making out on a swing, and at various other spots all over the globe