In the Deathstalker series by Simon R. Green, Hazel D'Ark eventually learns to summon variants of herself from alternate universes. This goes horribly wrong when she's captured by the Blood Runners, who force her to summon those constantly, killing each one in hideous ways.
A teenage boy finds a duplicating device in William Sleator's The Duplicate, and uses it so he can go on a date and his grandmother's birthday party at the same time. Hilarity Ensues when his duplicate claims to be the original, and ends up going on the date while he gets the birthday party. Then the duplicate makes another duplicate, and things start getting complicated.
Even more so as it turns out that the alien device put an automatic time limit on any duplicates - not only do they become more erratic and homicidal but they self-terminate after a certain period of time regardless of whatever else they do.
This is the key SF element in Brin's Kiln People. The original copies himself to a number of specialized golem bodies to perform various chores. Sometimes the copy isn't clean and it "goes Frankie" and takes a vacation instead of buying groceries.
Within the world of Who Censored Roger Rabbit?, all Toons can summon a "dupe" which will disappear in 24 hours. They're typically used for stunts and to allow for Amusing Injuries. The Roger Rabbit who comes to Eddie Valiant is a dupe of the original trying to solve his murder before he disappears.
Meow's A Crowd in Whispering Nickel Idols, in which the semi-divine litter of kittens known as the Luck of A-Lat appear to consist of five or six most of the time, but can fan out by the hundreds when there's a whole crowd of people to interact with and influence the temperaments of.
In Philip K Dick's short story Upon the Dull Earth, protagonist Rick watches his girlfriend Silvia get killed by giant supernatural angel-like creatures whom she has previously been able to summon through animal sacrifice. Rick is able to contact these creatures and bring Silvia back to life, despite their warnings that something might go wrong. Gradually, everyone Rick encounters turns into Silvia, including Rick himself by the end of the story.