 After viewing initial dailies, the director, Jonathan Mostow (qv)  deemed Sophia Bush (qv) too young to play hero John Conners love  interest, and replaced her with Claire Danes (qv) at the last  minute. Danes started filming immediately and basically learned  about her character on the job. Danes later said this may have  helped her performance, as Kate Brewsters character was similarly  thrust into a strange new reality with no warning.