In the episode called "Haunted House", Clarissa's aunt, Aunt Mafalda comes from Ottawa, Canada to visit the family. Elizabeth Tess, who portrays Clarissa's mother Janet Darling was born in Toronto, Canada.
In the pilot episode, Marshall says after Sam goes out the kitchen window "Why doesn't that boy ever use the door?" Sam during most of the show's run, used Clarissa's bedroom window to enter the house.
Marshall Darling: [after Ferguson hid Clarissa's bike as a joke, and it disappeared]
Well, Ferguson, if it's really gone and you can't get it back, you know what you gotta do.