First contact with the Cytherians, who explore by bringing others to them and who transformed Reginald Barclay into a genius so that he would deliver the Enterprise-D.
In The Next Generation episode The Nth Degree, the Enterprise-D investigates an unknown probe near the failing Argus Array telescope. The probe floods a shuttle with light and knocks out Lieutenant Barclay. He wakes confident and astonishingly clever, and before long is repairing the array single-handed and debating physics with a holographic Einstein.
When the ship's computer proves too slow for him, Barclay links his brain directly to it through the holodeck and cannot safely be removed. He then creates a subspace distortion that throws the ship thirty thousand light years to the centre of the galaxy.
There a huge, genial face appears on the bridge. The Cytherians have no wish to travel; they reprogramme visitors' machines, and this time a person, to bring newcomers to them for an exchange of knowledge. After several days they send the ship home, and Barclay is himself again.