Alexander Siddig (Dr. Bashir from Star Trek: Deep Space Nine) and James Callis (Dr. Gaius Baltar from the new Battlestar Galactica). I thought for a while (until I looked up Callis) that Siddig had a younger brother who had also decided to act in a sci fi series.
Peter Coyote (in ET especially) and Henry Fonda.
Capt. Janeaway and Katherine Hepburn
MiM
whoa. He really does.
William Devane also sounds alot like Jack Nicholson.
Mary Kate Olsen’s voice is nearly indistiguishable from Ashley Olsen’s voice.