Both involve undercover cops trying to take down drug dealers.
Both dramas begin with a different case from a few years ago.
Both leads get help from a former friend.

Both dramas are about cops and drug dealers. Both dramas have former cops who try to solve the case. Both show the development of a friendship as they learn to trust each other.

Both of the female leads are actually the last princess from a previous dynasty. Both of them fall in love with the emperor. My Bratty Princess has a happy ending, while Legend of the Dragon Pearl doesn't have as great an ending.

Both dramas use the comical acting style for lots of laughs.
Both dramas merge an ancient drama with the modern world.
In K.O.3an Guo there are different dimensions and one of the dimensions takes you to a historical past setting.
In Your Highness, they are in a gaming world that is set in a historical setting.
Both dramas include a villain with a hidden identity.

Both have characters experiencing some kind of time loop.
Both have characters who die only to wake up again to try and figure out how to change the ending.

Both cdramas depict life in high school with secret crushes and friendship. Both male leads are great basketball players and admired by their classmates. Both male leads act so cute when they are jealous.

Both dramas depict a love that crosses boundaries into another realm to change the past and the future. Both dramas has a lead that almost disappears from existence while trying to save the other lead.

In both dramas the female lead tries to change the outcome of the story. In A Girl Like Me, Ban Hua gets dreams that predict the future. She tries to change things based on her dreams. In A Twisted Fate of Love the female lead actually goes back to the past to attempt to change the outcome. Both dramas have sinister plots that affect the emperor and the court.

Both of the dramas take place in historical times and involves multiple detectives solving many mysterious crimes. Both dramas begin with two detectives competing to solve a crime and end up being friends. Both dramas include crimes that are connected to the palace and the emperor.

Both of the dramas include a secret love.
In Our Secret, a high school student falls in love with her desk mate and follows him to college.
In My Unicorn Girl, the girl ends up falling in love with her roommate since she enters college pretending to be a boy.

Both dramas have cops going undercover to break a drug dealing operation.
Both agents have super fighting skills.
Both agents fall in love during their undercover work.
Both agents almost die trying to accomplish their mission.

Both dramas portray a cop who goes undercover to break a drug ring.
Both agents get help from other civilians to help them accomplish their task.
Both dramas have seemingly dirty cops who complicate their task.