What villains that began either as background characters or one episode only characters went on to become recuring villains. At the very least what background villains went on to headline an episode. Basicly what villains were promotions in importance.
Here are some that come to mind. Some of these are inside information, others are such speculations by how the respective series progressed.
The H.I.V.E. (Teen Titans) - they were only suppose to be the main villains in Final Exam and never really be seen again. Maybe they were intended to come back, but not as much as they would appear in the series nor really be centeral villains in any epsiodes again. They were suppose to be Slade's pawns, and never be seen again. Gizmo appeared later in the season, and again in season 2. Before they returned in season 3, and appeared quite frankly. Not to mention they were the most recuring characters in Teen Titans Go and our extremely popular in the world of Fan Fics. I am sure when they wrote Final Exam they didn't invision any of that.
Mumbo Jumbo (Teen Titans) - suppose to be a background character, and never play a central role in an episode. Finally got an episode to himself in season 3 in Bunny Raven Or How To Make a Titananimal Disappear.
Professor Domentor (Kim Possible) - he was suppose to just be a rival for Drakken, not a real KP villain. Similar situation to Mumbo Jumbo, he is a villain that Kim never got around to fighting because Drakken showed up. Until season 3 when he got to be the main villain in an episode, and in season 4 got his own plot of trying to steal Kim's battle suit.
Here are some that come to mind. Some of these are inside information, others are such speculations by how the respective series progressed.
The H.I.V.E. (Teen Titans) - they were only suppose to be the main villains in Final Exam and never really be seen again. Maybe they were intended to come back, but not as much as they would appear in the series nor really be centeral villains in any epsiodes again. They were suppose to be Slade's pawns, and never be seen again. Gizmo appeared later in the season, and again in season 2. Before they returned in season 3, and appeared quite frankly. Not to mention they were the most recuring characters in Teen Titans Go and our extremely popular in the world of Fan Fics. I am sure when they wrote Final Exam they didn't invision any of that.
Mumbo Jumbo (Teen Titans) - suppose to be a background character, and never play a central role in an episode. Finally got an episode to himself in season 3 in Bunny Raven Or How To Make a Titananimal Disappear.
Professor Domentor (Kim Possible) - he was suppose to just be a rival for Drakken, not a real KP villain. Similar situation to Mumbo Jumbo, he is a villain that Kim never got around to fighting because Drakken showed up. Until season 3 when he got to be the main villain in an episode, and in season 4 got his own plot of trying to steal Kim's battle suit.