My Mom

Synopsis
When Mordecai and Rigby fail at another task, Benson has Muscle Man and High Five Ghost supervise them. Mordecai and Rigby hate having to put up with Mucle Man and High-Five, especially Muscle Man's "My Mom" jokes. After spending the day with them, Mordecai and Rigby decide that they are very fun to be around. Mordecai still cannot put up with Muscle Man's jokes, however, and tells him that he doesn't say the joke right. Mordecai proceeds to tell "Your Mom" jokes, and Rigby soon joins in. Muscle Man becomes infuriated and calls on his brother to teach Mordecai and Rigby a very important lesson.

Plot
Mordecai and Rigby dash from a nursery to deliver a lemon tree to Benson. However they destroy the lemon from rushing there, making Benson furious. He tells them that he is sending Muscle Man and High-Five Ghost to supervise them while they get a replacement lemon tree, and they will supervise them over and over again if they keep messing up, much to the dismay of the duo. As Muscle Man and High Five Ghost come over, they travel by cart to the nursery, however, Muscle Man passes it stating he knows a shortcut. In reality, they go to get tacos for a lunch break from Muscle Man's friend at a Taco stand.

After lunch, they and High Five Ghost upgrade the engines in the cart to make it go considerably faster. They blaze through a forest to arrive at the nursery. Despite Mordecai's insisting that they need to get the lemon tree to the park, Muscle Man tells them to "chill out." They hang out and play arcade games. Mordecai and Rigby almost start to like Muscle Man, except of his abundance of 'my mom' jokes. After Muscle Man tells another one, Mordecai states he's telling the joke wrong and the jokes are supposed to be about the other person's mom, whereas Muscle Man makes fun of his own mom.

Muscle Man gets enraged by this, thinking Mordecai is making fun of his mom, and calls his brother. Suddenly, a crack emerges from the ground and a truck covered in flames comes out. Muscle Man's brother comes out and answers his brothers call. He takes out a picture of their mother, and tell Mordecai and Rigby to kiss it. Then they place it on a grill, light a match, burning the photo and make Mordecai and Rigby eat it, much to their dismay.

After they eat it, they find out it was a joke and that the photo of Muscle Man's Mom was actually a picture of his butt but with make-up to make it look like his mom. Benson comes back and congragulates Muscle Man and High Five Ghost. Mordecai grumbles "I hate Muscle Man". Rigby asks if he knows who really hates him (a reference to the jokes that Muscle Man make).