Mordecai shares a room with his coworker Rigby. He seems to be the more mature of the two, and is sometimes put off or frustrated at Rigby's creativity and unwillingness to keep their jobs. This is further supported in the episode "The Power", in which Rigby punches a hole in the wall and suggests hamboning to make Benson give them raises so they could pay to fix it. It appears that he is stronger than Rigby, as seen when they play punchies. He always beats Rigby (though he fakes losing at the end of "Death Punchies" episode).
As proven in "Grilled Cheese Deluxe", Mordecai is a better liar than Rigby because Rigby told the truth to Benson about the grilled cheese deluxe but he didn't believe him so Mordecai lied that they "ran over it by accident."
Mordecai is usually more mature than Rigby as shown in many episodes. He has a crush on Margaret Smith although she doesn't notice it. He can be angry at Rigby for being a idiot like in "Meat Your Maker", he snapped because Rigby can't fix anything so he said "you pissed me off". Mordecai is also a slacker like Rigby plays video games other than working. In "Brain Eraser", he saw Pops naked so he would do anything to get that memory removed.
Mordecai is a blue jay although he isn't seen flying. like birds, he has a beak to talk. Mordecai is tall with arm-like wings. He is light blue, black and white. He has three feathers on the back to act as a tail. And his legs are long and have two toes each foot.
- Rigby: has been Mordecai's best friend ever since they were kids as seen in a flashback in the episode "Don". They usually play video games and slack off together instead of working. However, Mordecai can be angry at Rigby at times such as in "Grilled Cheese Deluxe" when Mordecai got in a bet with Rigby on who would win on a lying contest. But still Mordecai says Rigby is like a brother to him.
- Margaret: is Mordecai's main crush in the show. She is a close friend with Mordecai but doesn't know he has a crush on her. In "It's Time", Mordecai has tried to ask Margret out to watch Pajama Sisters 2 but he doesn't know to talk to girls.
- Benson: doesn't like Mordecai because he usually slacks off instead of working. Although Mordecai doesn't get in trouble more often than Rigby.
- Muscle Man: Mordecai doesn't really like Muscle Man that much mainly because of his "My Mom" jokes. This is proven in "My Mom" when Mordecai gets annoyed by Muscle Man's jokes.
- "Hmm Hmm"
- " You're jinxed! "
- Mordecai is a blue jay, although, he doesn't seem to be able to fly.
- Mordecai has a huge crush on Margaret, but falls apart whenever he tries to talk to her. In "Caffeinated Concert Tickets", he goes to the Fist Pump concert with Rigby solely because Margaret will be there.
- In "Meat Your Maker", his infatuation is furthered evidenced by a fantasy he had while in a hypothermic coma in which he and a bikini-clad Margret were alone together on a tropical island.
- He is voiced by J.G. Quintel, the show's creator, in which he uses his natural voice.
- Quite some time before Regular Show's premiere, Mordecai and Benson each made a cameo appearance in the short subject 2 In The AM PM.
- Mordecai is notably good at video games, winning a game called Hats 4 Sale ten times in a row.
- Another example is that he always wins in "Dig Champs".
- He has mentioned that he always wanted to date a girl named "The Power" although in later episodes wants to date Margaret.
- Mordecai has learned more Death Kwon Do moves than Rigby as proven in Death Punchies.
- In the episode "Don", it is revealed that he and Rigby were best friends when they were little kids.
- It is revealed that both he and Rigby are 23 years old in "The Power".
- In the episode "It's Time", Mordecai kills Rigby out of complete jealousy and rage by pushing him off a microwave traveling through time and space, literally turning Rigby into star dust, and is not seen in the episode again until Father Time gives Mordecai a do over.
- He doesn't get into as much trouble with Benson as Rigby.
- He knows Rigby can't watch scary movies because the last time they did Mordecai had to walk him to the bathroom for a week.
- In the episode "Peeps" he is good at a staring contests, and Mordecai played against Peeps and won but had to go to the hospital when he couldn't blink.
- Mordecai has seen Pops naked in "Brain Eraser".
- Mordecai and Rigby tried to returned a game named The Realm of Darthon because they think it sucked
- Mordecai and Rigby were second in Cartoon Network's best duo of 2010, only to be surpassed by Adventure Time's Finn and Jake.