When Harry Decides to Be With His Friends No Matter What; The 1st Slughorn Reunion in the Train

In book 6, Romilda Vane asks Harry if he wants to go with another people and not with Neville and Luna, Harry tells her that "no, I will stay with my friends" and Romilda & company go angry. Neville, who was looking for Trevor under the seat, crouching down and putting his legs and butt back, after a while, he found his toad.

In the same journey to Hogwarts, Slughorn made a little party in a compartment with specials students he knew: Cormac McLaggen, Blaise Zabini, the Slytherin twins, Harry Potter of course, Hermione Granger (Harry had told Slughorn about her), and Ginny Weasley (who Slughorn had seen her, doing a marvelous defensive spell). Ginny, that barely had a little space to sit, told Cormac to let some space; Slughorn warns Cormac that if he was him, he would let her some space because Ginny could do the defensive spell to him.