They each deal with solving crimes and busting the bad guys. In both Signal and Lookout (Th Guardians) there are several main characters that work in a team and have very deep, heart-wrenching backstories and goes/focuses on each their individual stories equally in different segments of the drama. Sooji and Haeyoung have strong similarities regarding the crimes that changed and ruined their lives. The villains are especially vile and will make your blood boil in both, LOL.

While Lookout is not as superb as Signal (among my top faves!), I still strongly recommend it because it is good and have paces that will have you on the edge of your seat until the very end.

-Both female leads have similar personalities & life circumstances
-They involve family dynamics/children
-The mothers of the female leads are strong-spirited in both

They overall just have a similar feel to them!These are my top two dramas EVER & remind me of each other! Trust me and just watch them... ;)