Agents Turned Odd
- Odd Todd- Let oddness happen, created odd-causing gadgets, and released a Pienado. This all led up to him not being allowed to be part of Odd Squad.
- Olga- Stole half of everything.
- President Obbs- Tried to take over the world by mind controlling Odd Squad scientists.
- Weird Tom- Stole Odd Squad papers including gadget plans. He then forced Odd Squad to shut down in an act of revenge for not being allowed to become a full-fledged agent.
- O'Duffey- Worked for Party Pam for a little time.
Undercover Agents, Betrayed the Villains
- Evil Mime- O'Donahue, to figure out what the Evil Mimes were doing and to stop them.
- Patternista- Ms. O testing Oprah if she could take her place.
- Kooky Clown- Olive, to win back Odd Squad tube map.