Maris is the wife of Niles (and ex-wife towards the latter end of the series', and is never actually seen, although she was once mistaken for a hat-stand by Frasier, who only realised it was her when he noticed the hat-stand moving.
Profile (by Howard Gensler - TV Guide, August 5, 1995)
Name: Maris Crane. Age: 40, on more than one occasion. Children: None, for goodness' sake. Father: A yachtsman ("the Commodore") with only months to live. Household income: Rich. Make that filthy rich. Appearance: Small and slender, with a wan complexion. Or, as Frasier puts it: "Bleached, 100 percent fat free, and best if kept in an airtight container." Demeanor: Frosty, and not as in "...the Snowman." Hobbies: Sensory deprivation, plastic surgery, fencing, interpretive dance, and the Women's Senior Yoga Group ("old money in bodystockings," says Niles). Kept several prize topiaries until Yoshi the gardner emasculated them during a drunken trimming spree. Always dreamed of being a ballet dancer, but according to Niles, "The poor dear could never get her weight up enough." Clubs: Won election as wine club president when her photos from rival Matthew Pym's wedding showed the label on the champagne he served. Worked tirelessly in a failed attempt to get Niles into Seattle's prestigious Empire Club by cultivating relationships, rumor-mongering, and accidentally dumping crabmeat into the cleavage of another candidate's wife. Charitable endeavors: In the coming season, Maris will contribute to the care (at least the hair care) of a foreign foster child. Medical history: Hypoglycemic, allergic to roses, and unable to produce saliva. Unusually rigid vertebrae, and quadriceps so tight she can't straddle anything larger than a Border collie. Views on romance: Does not trust unconditional love. Requires proper motivation (read: nice new Mercedes) to get in the mood. Defense mechanism: A pearl-handled revolver she keeps under her pillow. Appeal: "Maris is a wondrous distillation of many essences," says Niles. "It's as if you could take a great French cathedral, a painting by El Greco, and the upper third of Norway and magically transform them into one tiny woman with ferret eyes and disturbing hair."