Ben 10: Omniverse (2012)

S7E5 Fight at the Museum

Ester invites Ben to a museum exhibit showcasing alien artifacts, but she’s less than thrilled when he brings Rook along. To her surprise, they run into Ben's old crush, Kai, sparking immediate jealousy in Ester. Their dynamics shift when a valuable exhibit that Kai organized goes missing, forcing the four of them to band together to solve the mystery. Meanwhile, Chrono Spanner makes another appearance, attempting to sway Ben into believing he’s fated to marry Kai, much to Ester’s irritation.