Mario Marconi first appeared in Episode 25, though we heard of him through Dr. Rick Edison for several months before.  Rick was terrified of Marconi and considered him a threat.  Marconi first appears as an Igor that was willing to work for Dr. Bob Tesla for free but, throughout the episode, items kept disappearing, secretly being stolen by Marconi.

When Rick comes in to kill Igor, Marconi shows his true self to a now terrified Edison.  Marconi confesses that he had been trying to break into Dr. Bob Tesla’s terminal to steal all the inventions he has but had not been able to decipher the password.  He pulls out the Di-clotron , which he had stolen the plans of from Rick. This causes Rick and Dr. Bob to come to a temporary truce to deal with Mario. Dr. Bob, after finding out they were Rick’s plans for the Di-clotron, refused to help Marconi, telling him to do his worse.  When he attempted to shoot Rick and Dr. Bob, the Di-clotron fell apart in his hands and he ran away.

In Episode 28 Mario stole Nikola Tesla he was hoping they could team up and create new inventions, but upon discovering he could not understand Nikola he returned him to Dr. Bob.  As he leaves he kidnaps Kitty She-gor.

In Episode 32 Mario and Rick decide to start a partnership, when he leaves he promises to return Kitty She-gor which he had kidnapped in Episode 28.  But they immediately decide to attempt to steel Dr. Bob’s inventions, but when C.I.T.T. builds a Death Ray they decide to leave.

In Episode 33 Mario has returned Kitty She-gor, but Dr. Bob thinks there is something wrong, Mario has planned both poison and a bomb in Kitty She-gor, unfortunately Dr. Bob had only found the bomb.  Angry that Mario has now killed Kitty She-got he has C.I.T.T. get rid of him.  Once C.I.T.T. confirms that Mario is the owner of the Lamborghini Egoista that is taking up 2 handicap spots, he prepares to nuke the car from orbit, causing Mario to flee in an attempt to save his car.

In Episode 41 Mario and Rick arrive asking Dr. Bob if they can have a skull, but while Dr. Bob is the lab trying to find them one Mario knocks out Igor, and yanks out his skull.  Rick comments “this is dark even for us” Mario “I’m having a good time.”  But when Dr. Bob sees what they have done he bans them both from the theater and chases them out.