He is the co-leader of 4DR.
He first debuted in Into the Fourth Dimension. He appeared fairly early on with all the others to help look for the D-Stars. He was MarioMario54321's counterpart, as such, when MarioMario got controlled, QuarioQuario was knocked out for a large amount of time. At the end, QQ54321 helped the others save the Fourth Dimension.
He has appeared in various bloopers and videos involving the Fourth Dimension.
He had a cameo in Blooper 40 where he cheered Starman3 on to get up.
His next appearance was Blooper 44, telling MarioStar to forget about the events that happened in Into the Fourth Dimension, which MarioStar referenced.
He only made a cameo in the form of singing the "Follow the Rainbow Brick Road" song. He also explained to the heroes that they get to the Rainbow Colonies by the D4 train.
- Mushroom Kingdom/Blooper Land counterpart: MarioMario54321
- Star World counterpart: StarioStario54321
- Crown Dimensional counterpart: QuinarioQuinario54321
- Dimension X counterpart (doppelganger): OiramOiram12345