Mordecai and Margaret finally kiss, but Mordecai is left disappointed after it was cut short by his bad breath, and wants to go back in time to redo it.
Mordecai, Rigby, Margaret and Eileen drive to the park after watching the movies. When they get to the park, Mordecai says he forgot his wallet in Margaret's car, so he goes back to find it. A couple seconds later, Margaret shows up, and tries to help him find his wallet. They kiss, but Margaret pushes Mordecai away because his breath smelled bad from a chili dog he had earlier.
Embarrassed, Mordecai grabs Rigby and runs inside the house. Mordecai says that him and Margaret were in the moment, and they kissed, which Rigby doubts. Mordecai says that his breath smelled bad, and that he would be embarrassed forever. Rigby then pulls out a 'time machine', which Mordecai doesn't believe works. After fiddling around with it for a while, they press a button and machine sends them 15 minutes in the past.
In the past, they see a past Mordecai running to the car. They press the time machine's button, sending them further into the past. They try to prevent Mordecai from eating smelly foods, to stop him from having a bad kiss. They eventually end up going back to that morning when Mordecai was in the bathroom. They try to force the past version of Mordecai to use mouth wash, but when he doesn't believe the present Mordecai and Rigby's story, he takes the time machine from them and goes into the future to kiss Margaret.
Thankfully, Rigby has another time machine, which he says that he got $3 off for a double order, and they follow the past Mordecai. While travelling through time, there are a lot of appearances from previous episodes. Mordecai tricks past Mordecai so that he can keep him from kissing Margaret.
They finally reach the past Mordecai, and Rigby uses one of the time machines to take him to the future. Then present Mordecai and Rigby break the time machines, causing everything that just happened (between his first time travel to the machine's destruction) to have never happened, and time is set to where Mordecai is in Margaret's car. However, Mordecai doesn't want to have a bad kiss and realizing his breath is still bad, he abruptly finds his wallet, stopping Margaret in mid kiss. They get out of the car to join Rigby and Eileen (to have shakes). The episode ends with them entering the house, leaving Mordecai without a kiss from Margaret.
- Past Mordecai
- Muscle Man (mentioned)
- Movie Shack Hut Employee
- Future Mordecai and Future Rigby
- Mordecai and Margaret share their first kiss, which is undone at the end of the episode.
- The events of "Mordecai and the Rigbys" are mention when Past Mordecai claims that guys from the future lie.
- When Mordecai and Rigby are traveling through time to catch past Mordecai they visit several different times from several different episodes.
- The Stag-Man watching Mordecai and Rigby from "Camping Can Be Cool."
- Rigby bumping into the Movie Shack Hut Employee from "Ello Gov'nor."
- Pops serving cotton candy to zombies from "Grave Sights."
- Future Mordecai and Future Rigby watching their past selves from "Mordecai and the Rigbys."
- Mordecai holding onto a chair while being attacked by the Destroyer of Worlds from "Just Set Up the Chairs."
- Even though Mordecai and Rigby destroy both Time Machines they use the same Time Machine again in "Exit 9B."