The Cutie Mark Crusaders tracking down what's left of Trixie's stuff (from the Ursa incident) in the junkyard and returning it to her. Especially as this included the gem her grandmother had given her as a good luck charm as a filly.
For that matter, all of Trixie's interactions with her grandmother; she seems to be the only one who actually cared about her when she was a child.
The Mane 6 and Derpyflying out into an enormous desert during a tropical storm to find Trixie.
In the final battle with Checker, the Mane Six create dream avatars to protect them and help in their fight against her. Twilight conjures up her brother, Shining Armor.