Pinch Thomas debuted on April 24, 1912, playing for the Boston Red Sox at Fenway Park I; he played his final game on June 19, 1921, playing for the Cleveland Indians at League Park II.
Pinch Thomas played in 24 games at catcher for the Cleveland Indians in 1918, starting in none of them. He made 85 putouts, had 24 assists, and committed 6 errors, equivalent to .25 errors per game (estimate based on total games played in). He had one double play.
Thomas Diamond debuted on August 3, 2010 and played his final game on October 3, 2010.
Thomas Field debuted on September 11, 2011 and played his final game on September 28, 2013.
John Kennedy ... he was a pinch runner on April 22, 1957 against the Brooklyn Dodgers.
It's perfectly permissible to play in a game even if you are not on starting lineup card presented to the opposing manager before the game. However, if a player does so, at least one other player must be permanently removed from the lineup, and that latter player may never play any part of the game. A player can come off the bench as a relief pitcher, pinch-hitter, defensive replacement, injury replacement, or a pinch-runner (the latter is fairly rare).
NBA player Adonis Thomas played for Memphis.
NFL player Thomas Davis played for Georgia.
NFL player Josh Thomas played for Buffalo.
NFL player Thomas DeCoud played for California.
NFL player Mike Thomas played for Arizona.
NFL player Eric Thomas played for Troy.
NFL player Donald Thomas played for Connecticut.