Makiguchi Katashi, personal guard to the Godaime Kazekage, woke up five years before the failed invasion that changed everything for Suna. Unsure if he was trapped in a genjutsu (they'd been fighting crazy Sharingan wielders after all), he went through his day per usual before realizing one thing. His best friend was killed by his then-yet-now crazy Kage today. So genjutsu or not, he had to try. He failed, but that was okay. Because his then-not-now crazy Kage had woken up disoriented too. And it wasn't a genjutsu.

Thirty year old Kakashi was supposed to have been killed by Pein during the Invasion. Instead, he wakes up in the body of his twenty year old self. (It gets a lot more complicated.)

Originally, Gaara thought the plan - brought to him by a desperate and shaken Naruto on the last holding place of the world's few remaining shinobi - was both insane and impossible. No one ever accused Gaara of being sane, nor sensible, so he agreed anyway. He hadn't really expected it to work.

Obito gets lost on the way back to the afterlife.

Kakashi is being trolled. He doesn’t know how that can be, but he knows with utmost certainty that he’s being trolled somehow. OR Kakashi gets saddled with the cheekiest little brats ever and wonders if it's too late to become a missing nin.