Wait, if Terezi was just fucking with him about the dragons, then what DID change the timeline?

He stopped Aranea from getting the Ring of Life (which prevented the events of Game Over from happening), he honked a horn and Terezi caught Gamzee and tied him up (which stopped Karkat from pacifying him and becoming his moirail), he wrote a note to Terezi saying he suggested that she not date Dave, (which she didn’t) and John stopped her from killing Vriska (this resulted in Vriska going on the meteor trip with everyone and her and Terezi eventually becoming moirails).