Mark is the only member of NCT Dream who experienced graduation from the group. NCT Dream originally operated under a graduation system: members were expected to leave when they turned 20 in Korean age and could then focus on other NCT units or activities.
Mark debuted with NCT Dream in 2016 and graduated in December 2018 after reaching the system's age limit. He later returned to the group in 2020, when SM Entertainment abandoned the graduation concept and converted NCT Dream into a fixed-member unit.
The other original members—Renjun, Jeno, Haechan, Jaemin, Chenle, and Jisung—were therefore never formally graduated. A common mix-up is assuming that Mark permanently left NCT Dream; his departure was temporary, and he has remained part of the group's later activities and releases.