Walter Koenig played which part in the Star Trek series

Ensign Chekov
Walter Marvin Koenig (/ˈkeɪnɪɡ/; born September 14, 1936) is an American actor, writer, teacher and director, known for his roles as Pavel Chekov in Star Trek and Alfred Bester in the Babylon 5 series.

He wrote the script for the 2008 science fiction legal thriller InAlienable.

Read more...https://en.wikipedia.org/wiki/Walter_Koenig

More Info
www.walterkoenigsite.com — Official Site

Chekov's Enterprise: A Personal Journal of the Making of Star Trek