You can find this in JTBC Drama YouTube channel.
Initially there are 6members playing the fun game but later there is a surprise guest that is Han so eun who played young jung da jung
The first part of game is to choose one of the two options for each question thrown onto every member.
With every question and answer there is some amazing conversation and opinions about the real world.

When the guest arrives the twins respect, for Han so eun and Do hyun is amazing.I love how the si-ah and si-woo still call her as EOMMA and Do hyun as APPA outside of the drama. They were so joyful to meet her.
Infact other than Do hyun nobody had scenes with her so it was first meeting for all of them.

There is the second part where a lie detector is used. The cast is given a yes/no question and they have to answer while placing their hand on lie detector. This part is also very fun to watch.
Hwang In Yeop literary keeps the atmosphere more vibing with their his statements. And yes he is actual 18again person.