Episode 8 , 1h:18min:14, When that guy says " the code is 0070" Do you guys remember ?? it s a "Fight for my way " reference, when Kim Ji Won says that to Park Seo Joon !!!

Episode 11 , when they show two Kim so hyun , it feels like a reference to his noir movie "Real" , where he plays a doppelganger!!

Here's a partial list of references which people mentioned in the comments:

I noticed Hyun Woo, while window shopping in Germany, pick up a flower pot similar to the Edelweiss from CLOY which Jung Hyuk gifted to Se Re. (I'll update this with the episode and timestamp, later.)

Hyun Woo's Suzy smile… (??)

Someone mentioned Vincenzo was using the pen gifted to him by Cha Young

And another comment mentions Hae In's mom was watching CLOY in ep 4,

@Tom mentioned that there was also a My Liberation Notes nod on the subway in ep 8.

@10years noticed Beom Ja's line, "that guy looks like Leslie Cheung" and that the actor played the role of Leslie Cheung’s ghost in a small indie Korean movie.

@OfftoDramaLand caught the way HI waved bye to BHW outside their countryside front gate was similar in CLOY to how Captain Ri awkwardly waved back at Yoon Seri in North Korea.

Oh my god! The fight for my way code thing I noticed too! Also, when hae in said she’ll come back as an angel reminded me of kjw’s scene in descendants of the sun where she goes to jin goo’s ex’s wedding and tells him she looks like an angel.

 Star Rover:

Here's a partial list of references which people mentioned in the comments:

I noticed Hyun Woo, while window shopping in Germany, pick up a flower pot similar to the Edelweiss from CLOY which Jung Hyuk gifted to Se Re. (I'll update this with the episode and timestamp, later.)

Hyun Woo's Suzy smile… (??)

Someone mentioned Vincenzo was using the pen gifted to him by Cha Young

@Tom mentioned that there was also a My Liberation Notes nod on the subway in ep 8.

@10years noticed Beom Ja's line, "that guy looks like Leslie Cheung" and that the actor played the role of Leslie Cheung’s ghost in a small indie Korean movie.

@OfftoDramaLand caught the way HI waved bye to BHW outside their countryside front gate was similar in CLOY to how Captain Ri awkwardly waved back at Yoon Seri in North Korea.

yessss the Liberation note oneee ,, i forgot to mention it. ...ngl when that subway scene was on ,i was waiting for them to show that billboard that said " something good will happen to you today" ??too bad they didnt

Anyone catch in episode one during BHW's interview, he describes what HI looks like when she came out of the helicopter in his country bumpkin town. He says she looked like an angel descending, Korean word kang-lim. Back in CLOY, before RJK and YSR had to separate at the demarcation line in North Korea, she said dont forget me. He says how can i forget someone who felll from the sky? She said, I didn't fall, Kang-lim.  I descended  (like an angel)

Ep 15. Aunt Beomja confessing her love on speaker, is a reference to Song Hye Kyo s confession in  "Descendants of the sun"

In episode 15 the Private eye was interviewing some goofy type spies that the family hired to look over Hae In  while she was in the hospital in Germany.  The female "spy", Hong Jin Kyung, was being interviewed and asked what she did in the past. She said, "I ran a comic book shop."  She was in Love from the Star as the FLs high school friend who owned the manga book shop.