From left to right, (Bruce, Brettski, and other non-MSTies) that's Tom Servo, Mike (Nelson), and Crow T. Robot. Tom and Crow are both robots built (in life and on the show) on a budget - Tom is mostly a gumball machine and Crow is a plastic bowling pin and a lacrosse mask (Chip Rowland could use him for structure).
MST3K ran from roughly 1988 to 1999, on KTMA (Minneapolis/St. Paul), Comedy Central, and the Sci-Fi Channel.