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The two trainees appeared on this episode as the avatars of a best friend duo who have been singing together for 3 years. 'Shadow Singer' consists of a format where unknown singers hide backstage, while enlisting the help of well-known celebrities as their avatars to go on stage in front of the panelists and the audience, to lip sync and perform for them. 

Ahn Hyung Seob and Lee Eui Woong, who were acting as the avatars of the vocal duo 'IDOL' for their performance, drew cheers from the crowd for their good looks. After their introduction, Youngji from the panel asked NU'EST's JR, "JR, don't you know them?" 

JR smiled mischievously and asked the duo on stage, "Haven't we met before?" to which Lee Eui Woong answered with laughter, "I don't really remember..."

For their performance, Ahn Hyung Seob and Lee Eui Woong lip sync-ed Lee Jang Hee's "A Glass of Memories", an energetic rock number. Check out the performance below!