Madison "Maddie" Rooney is the identical twin sister of Liv. Maddie also has two younger brothers and two parents that both work at the school she and Liv attend. Maddie is an outstanding student and school basketball phenomenon whose popularity is on the rise. That is until Liv makes a triumphant return to their Wisconsin High School. Maddie is more of a tomboy when compared to Liv.
- Her birth name is Madison.
- Maddie plays with her charm bracelet when she is nervous.
- "Bam! What?!" seems to be Maddie's catchphrase.
- Maddie and Joey are the only two people in their household to wear glasses.
- Maddie loves to win, and also likes to be competitive.
- It is unknown why Maddie and her twin Liv have blonde hair, while her parents and brothers have brown/black hair. It is unknown if they were adopted or if they inherited the blonde hair from a relative.
- The first time the girls pretended to be each other was when they were six.
- It is revealed that Maddie is the younger twin, as she was born on the 6th. Since she was born after midnight, this means the twins have separate birthdays.
- When she still thought she was born on the fifth, she made five her lucky number and put it everywhere, including all over her locker.
- She loves chicken pot pie.
- Her favourite restaurant is The Hoosegow.
- She is very sensitive at heart.
- She really, really, really likes her boyfriend, Josh.
- In "Home-Run-a-Rooney", she realizes making someone happy is more important than always winning. She even almost gave this up to be with Josh.
- She attends SCSU as of "Skyvolt-a-Rooney, after being offered a scholarship.
- She has a slightly deeper voice than her sister and cannot sing.