Demons from nightmares, intersting. Each of the Z-fighters could have a demon to fight and have to concure, active due to the residual negative energy left over from Omega Shenron. Pan could end up facing a version of Omega Shenron, seeing as she saw everyone struggle against him, lose and need saving, and be made to need diapers as a result of an injury to sevear to fully be repaired. An example of other nightmares would be Vegeta vs freeza, cause he never realy beat him in the first place, and he never will beat Goku, so...yeah