Seven as the "Midnight Snacker"
The Midnight Snacker was the name given to an individual who had raided USS Voyager's mess hall in the middle of the night on several occasions.
In 2375, the Snacker absconded with a leg of Kelaran wildebeest that Neelix had prepared for Ensign Ryson's birthday. At the briefing the next day, Neelix recommended that stronger security measures be taken. Tuvok suggested an armed security detail, but Neelix instead asked for permission to replicate locking mechanisms for the cabinet doors, to which Captain Kathryn Janeway agreed.
Unbeknownst to everyone, the Midnight Snacker was Seven of Nine, who was sleepwalking and manifesting a Klingon personality, that of the son of K'Vok. When The Doctor uncovered her identity, he was certain Neelix would be relieved that they now knew who was prowling around his domain. (VOY: "Infinite Regress")