After the success of his daughter's replacement, Dr. Sauerkraut builds several dozens of the Robot Girl, each one reflecting an aspect of the late daughter he loved.
Downplayed: Dr. Sauerkraut's daughter dies in a plane crash, so he adopts a little girl who survived in that plane crash, believing that it's the humane thing to do.
Dr. Sauerkraut sold his daughter to Space Aliens/The Devil/The Fair Folk in exchange for the secrets of his advanced robotic technology, and builds a replacement to stop people from learning what he did.
The poor doctor can't let go of his late daughter.
Dr. Sauerkraut builds the replica to prevent the death of the loved one in the first place, like a clone intended as an organ donor to save his diseased and dying daughter.
Who herself was a robot and created Doctor 2.0 by modifying her specs.
(fourth one down), despite Dr. Sauerkraut's initial objections, the replica says she's fine with being exactly like Sauerkraut's daughter, since that is what she was designed for; she can't be her own self instead because "her own self" is Sauerkraut's daughter.
(Sixth one down), brain damage from the accident means that the robot isn't his real daughter anymore.
The replacement is obviously a robot, sporting "robot ears" and a built-in plasma cannon.
Alternatively: His replacement goldfish is really a replacement goldfish.
Zig Zagged: Dr. Sauerkraut builds a robotic duplicate of his dead daughter which is composed of machine parts and the remains of his dead daughter's body.. That body is trashed beyond repair but the good doctor has a Heart Drive with the sum total of her memory and personality, which he places into a second robot body. Then background noise in the uploading process caused variations in her personality and she behaves differently. These differences however are ironed out as the robot enters the daily routine of the daughter's life.
Averted: Someone dies. No attempt is made to replace them.
Enforced: "Now, how are we going to shoehorn a robot into this Harem Series?"
The real one was in a coma beyond all hope for recovering. By some miracle she woke up, and called her dad out. A Cain and Abel relationship developed between the real daughter and the replacement, which ended tragically for everyone involved.
When people learn of Dr. Sauerkraut's success, they want him to build replacements for their dead loved ones. The doctor complies, the people get what they want— every single one of them. Thus creating a race of robots that can never live up to the originals and further depressing the body they were made for.
Dr. Sauerkraut is disappointed that the replacement won't grow up like a normal daughter. His mental imbalance grows, and he sells the daughter off.
The replacement Wangsts for a bit, but eventually gets over it and becomes her own person.
The real one was in a coma beyond all hope for recovering. By some miracle she woke up, and was promptly touched by her dad's (desperate) love for her. She accepts the replacement as her little sister. They lived happilyever after.
Dr. Sauerkraut uses Organic Technology to build the replacement so it would grows up like a human would. Due to his mental imbalance, he eventually forgets that the girl is not his real daughter.
Played For Laughs: Dr. Sauerkraut's daughter dies in a plane crash, so he builds a Robot Girl in her likeness to replace her. The problem is, he modeled the robot after himself, so it's really a boy who must crossdresses to please his eccentric daddy.