Though not among Hollywood's best known supporting actors, Casey Siemaszko (pronounced Sheh-MA-zshko) has worked with some of Tinseltown's most important directors. Born Kazimierz Siemaszko in Chicago to a Polish concentration camp survivor and an English dancer, Siemaszko started performing at age five with his father's dance troupe, the Kosciuszko Dancers.
As a young man, Siemaszko studied fine arts at Chicago's Goodman School of Drama and launched his professional career on the Chicago stage before moving to L.A. where it took him four years before landing a role in Class (1983). In 1985, he played 3-D in Robert Zemeckis' Back to the Future (1985); he later reprised the role in the 1989 sequel. Since then Siemaszko has worked with Steven Spielberg on an episode of Amazing Stories, with Rob Reiner in Stand By Me(1986) where he played a member of Keifer Sutherland's gang, and had a major supporting role in Mike Nichol's Biloxi Blues (1989). Siemasko's film career slowed considerably in the 1990s with notable roles in Gary Sinise's Of Mice and Men (1992) and in Lance Young's sexually charged Bliss (1997). ~ Sandra Brennan, All Movie Guide. 