It's the original Korean version of the show.
Both female actresses have to play the roles of two different people since she is playing twins.

Part of the same School series. Both mystery and youth centered.

Both main male character's lack something because of an event in their childhood.
In Stranger the main guy lacks emotions due to a brain surgery during childhood.
While in Dr. Frost the main guy has trouble sympathizing with other's due to an injury to his frontal lobe as a child.

Both show how corrupt the government can be. Both have some crappy Prosecutors who only think of themselves. In Remember - War of the Son it deals with Alzheimer's and in Duel one of the characters has memory loss.

Both are crime dramas. Both are science-fiction. In Tunnel the main guy is looking for his kid. In Duel the main guy is searching for his missing daughter. However the two have completely different storylines. Tunnel has the time traveling aspect and Duel has the clone aspect.

Both have two universes connecting. Circle is about aliens or seems to be and W was about a comic book dimension.

Both have to do with the mind/Psychology. Liar Game has less to do with the law than Dr. Frost does. Both drama's have at least one Psychopath present in them. Plot wise they aren't much alike, Liar Game's plot has a game show, whereas Dr. Frost involves the main lead working with the Police.

Both have to do with Psychology. Sometimes Psychopaths, more so in I Remember You. Both Main Leads play Professors. Both help out the Police with their intelligence. There isn't much romance in Dr. Frost, but there's some in I Remember You.

Both drama's are Time Period dramas. Both have an evil Queen. In SHR the Queen is more evil, whereas in Hwarang the Queen is more neglectful.

In Goblin the flashbacks in history are in the time period of Goryeo, in which Wang Yeo (Yo) is King. Wang Yo is a character present in Scarlet Heart Ryeo. I think it's very interesting to see Yo being portrayed by different people. Both drama's have very emotional plot-lines to them, definitely have tissues prepared if you watch them.

Same person wrote both dramas. Both have fantasy characters present in them. In Legend of the Blue Sea the main female lead is a mermaid and in You Who Came from the Stars the main male lead is an alien. Both drama's have the same female actress playing the parts of the female lead. There are a few other actors/actresses that make appearances in both dramas.

Cha Hakyeon (N) stars in both dramas. Both are web-dramas. Both are slightly confusing and short!