Yoo Jae Suk wasn't afraid to unleash his inner uncle fan while filming for the upcoming episode of JTBC's 'Sugarman,' squealing over IOI's grand appearance on the show.

'Sugarman' is the first time all eleven members of IOI guested on a variety program, something that fans--and Yoo Jae Suk--have been looking forward to for the longest time. Yoo Jae Suk proved that he's the ultimate IOI fan by shouting out each member's nickname, such as 'God Sejung,' 'Maknae Somi,' and 'Center Yoojung' as they appeared on the set one by one. 

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When IOI performed "Pick Me," Yoo Jae Suk nearly went full uncle fan throttle mode, burbling, "I can't believe I'm seeing 'Pick Me' right in front of my eyes!" Seeing such an overexcited Yoo Jae Suk, Yoo Hee Yeol quipped, "There is a rabid middle-aged man on set," while Kim Yi Na joked, "I think he's foaming at the mouth." 

This episode is scheduled to air on April 26 at 10:50PM KST.