Code Lyoko S02 E17 XANA's Kiss

"Get ready to virtualize."

Xana creates a ghost called a polymorphic specter, that can change its shape or form at will and doesn't need to possess a host, then uses it to drive a wedge between the group by having it kiss people while disguised as them. At the end of the episode Aelita kisses Jeremy to see how he'll react. He (predictably) freezes up.