The /invite command allows a pirate to invite another pirate into a building. They receive a pop up message in their Ahoy! panel with a button that whisks them to the building. It is also used to let a person that was planked from a shoppe or stall to come back in. Only owners, managers, or roommates of a building may use this command. A pirate will not receive invites if they have dnd enabled, unless the person inviting them is one of their hearties.
The invite command was added in a minor July 2005 bugfix release. Its counter-part command, /eject (which merged with /plank later) also came in the same release.
/invite <pirate name>