Here is a video with some of the findings we could spot.

Here are the original mission goals:
Mission 1. Find the wrong picture!
On the top of the two pictures, there's a number. Find that number of wrong pictures!
It gets harder so don't relax your attention even if it's easy in the beginning^^!
+ ??? How many wrong spots are there in the picture marked with '???' ? Find it out together!

Mission 2. Where's Orange Caramel?
They are hidden in places on different level than season 1! No more hints!

Mission 3. Find hidden 'Mr. Cho'!
Cho Seho made a surprise appearance in the music video! Where is he?
+Other two artists from PLEDIS are also in it as surprising guests~

Go here for the original version:
https://www.youtube.com/watch?v=rqSF_...
And music:
https://music.apple.com/us/album/four...