(Twitter)

IZ*ONE member Jo Yu-ri surprised viewers by joining Fromis_9 as a guest via a call during Monday night’s Blueroom livestream at Twitter Korea’s office.

Speaking to the group, Jo said in excitement, “I heard Fromis_9 is coming back tomorrow with Fun, and that’s why I’m here,” drawing laughter from Fromis_9 members.

Things had seemed business as usual during the livestream until the nine-piece band invited Jo.

Blueroom live had previously featured one act at a time but Monday night marked the first time outside the US that a guest had joined -- albeit voice only -- an official Twitter live broadcast.

Up to three guests can appear at the same time, adding another fun element to what is normally a conversation between artists and viewers, with the latter communicating via text.

The livestream had racked up over 200,000 views as of Tuesday.

By Yim Hyun-su (hyunsu@heraldcorp.com)