Most of the artworks shown are not in the Smithsonian collection. Some of the pieces shown are: (1) the oft-reproduced V-J day in Times Square by Alfred Eisenstadt, originally published in Life magazine, (2) American Gothic by Grant Wood (Art Institute of Chicago), (3) Nighthawks by Edward Hopper (Art Institute of Chicago), (4) Crying Girl by Roy Liechtenstein (Private Collection in Cleveland, Ohio), (5) Le Penseur (The Thinker) by Auguste Rodin (Musee Rodin, Paris), (6) La Petite Danseuse de Quatorze Ans (Little Dancer of Fourteen Years) by Edgar Degas (Royal Academy, London), (7) Balloon Dog by Jeff Koons (there are multiple versions, in different colors), and (8) Venus Italica by Antonio Canova (North Carolina Museum of Art).
Yes. Night at the Museum: Battle of the Smithsonian is a sequel to Night at the Museum (2006), which was based on a 1993 children's book The Night at the Museum by Croatian author Milan Trenc. The screenplay for Battle of the Smithsonian was written by /American comedian writers Thomas Lennon and Robert Ben Garant. It was followed by Night at the Museum: Secret of the Tomb (2014).