Number two starts when "the artifacts from the Museum of Natural History are boxed up and sent to the archives at the Smithsonian in Washington." Adams' character is "undetermined," but she will be a historical figure who has a crush on Larry (Stiller). I have to wonder if they haven't figured out her character, or are just keeping mum about it. It seems sort of silly to sign her on as a love interest without knowing which figure she'll play.
However, in case they need help, let's provide it. If Reese hasn't signed, it could be Amelia Earhart. Not Louisa May Alcott. Margaret Sanger? Harriet Beecher Stowe? Susan B. Anthony? Helen Keller would make things interesting (if done respectfully). But here is my pick: ultimate flag lady Betsy Ross. Who would you cast Amy Adams as?