Mona Lethal is a battle/fighting robot whom was a very popular robot for her design and strength. Robotboy fell in love with her for finding her attractive and when he heard that she was going to be on the Robo-Con he went there to see her. Then when he signed for the robot battles and won every single match he had to face towards her to fight with. At first he didn't fight to her because he liked her so much until he finally attacked her when she almost killed Tommy and Gus for stopping her from destroying Robotboy. And thus he defeated Mona while being super-activated.
It is unknown what really happened to her later but she can be seen repaired on the episode "A Tale Of Two Evil Geniuses" where she sits with her owner Ronald Rump.
She appears to have a pretty skinny body shaped like a bow with big eyes and blue lips.
- Apart her cameo in "A Tale Of Two Evil Geniuses" she also makes a cameo on the episode "Bad Language" on a CD-folder Robotboy received from Kamikazi.
- Her name seems to be a pun on the famous Italian painting, Mona Lisa by Leonardo da Vinci.
- She's also one of the villains Lola never met or mentioned.
- So far she has physically appeared in 2 episodes along her non-physical cameo on "Bad Language".