SEE ALSO: S.E.S Shoo surprises fans with mysterious countdown announcement

S.E.S members Bada and Shoo were guests during the episode and were preparing for an upcoming S.E.S 90s performance. As Eugene is currently pregnant, she was unable to join her fellow former members.

At this, the 'Infinity Challenge' members suggested that they call Girls' Generation's Seohyun to ask her to take Eugene's place. When Yoo Jae Suk added, "It's perfect because TaeTiSeo is promoting right now," she further expressed her confusion, saying, "Tae... You mean Seo Taiji?".

Her confusion amused all of the 'Infinity Challenge' members, and Jung Hyung Don told her, "Watch some TV!"

Bada then said, "You don't know Girls' Generation's maknae? She's the hoobae who's doing the musical with me," referring to their 'Gone with the Wind' musical. 

Shoo replied, "I don't know who Girls' Generation's maknae is. I didn't know [Bada] unni was doing a musical either," earning laughter from the set for her confused state. Shoo then commented, "You're saying she's an SM hoobae? Then that's fine," satisfied that they would be at least paired with someone from S.E.S's former label.