These little people are from the secret level in episode five. They just push you along. One shot stuns them. Some people call them Goplats, Scotties, or Koraths. They got the name Goplat from the well-known error that closes the game in easy mode in version 1.0 upon the entry of that level, but Goplat actually refers to a platform that follows a specific path, which is what caused the error.