|First appearance||"How Do You Solve a Problem Like Maris?" (4.01)|
|Last appearance||"Leo the Lion" (11.04)|
|Guest appearances||Maris: 16.02, 16.11, 17.11, 17.13, 18.22, 24.10, 24.13, 25.11, 26.04, 26.14, 29.01|
Leo Kingsley is a main character in the Frasier-based fan fiction spin-off Maris.
Leo is a sophisticated and cocky young go-getter who becomes the new cleaner at the start of Season 4. Despite working for minimum wage, Leo comes from a highly wealthy background and only took the job so he could prove his independence from his family. His father is Alexander Kingsley, Maris' chief social rival. Throughout his time on the show, Leo's father causes many problems for Maris and her servants. In a story arc that spans the end of Season 8 to early in Season 11, Alexander and Maris are involved in a series of cons together, which almost costs everybody their jobs. Leo ultimately decides he has had enough of his family dominating his life and departs the mansion to free himself from their influence.
Early in Season 5, it is revealed Leo is having an affair with Eve Summers. They part ways prior to the start of Season 6 after reaching the conclusion that their relationship is primarily based on physical attraction. It is also revealed Leo has an ex-wife, Mary, whom he married so she could avoid deportation. In Season 9, Leo almost re-ignites his spark with Eve, but nothing happens when she comes to the realisation that she has fallen in love with someone else. Outside of his on/off relationship with Eve, Leo is a bachelor for the majority of the series and remains single at the time of his departure.
In Season 8, Leo is shocked to discover he has a half-sister, Kelly Crane, a result of his father's long ago affair with Maris. Leo spends much of his time with Kelly trying to be a good older brother, having always had unpleasant siblings to contend with himself. After his resignation from the mansion, Leo makes sporadic appearances in subsequent seasons. The Season 18 finale sees Leo's discovery of another previously unknown half-sibling, the reclusive Charlie, whom Leo develops something of a rivalry with due to the favouritism displayed by their grandfather, Charles.