Lysa mentions Jon Arryn's death and the letter she sent Catelyn in "Winter Is Coming", in which she falsely blamed the Lannisters.
Sandor's comment that "tougher girls than you have tried to kill me" is a callback to Arya's attempts to kill him, either by hitting him with a stone on "Second Sons" or by stabbing him with Needle on "First of His Name".
Olenna comments that the gold mines in the Westerlands have run dry. Tywin said that in "First of His Name".
Jon tells Jorah that the mutineers who killed Jeor Mormont found justice.
The Hound repeats his wish to kill his brother. Sansa accuses Littlefinger of conspiracy to murder Jon Arryn, by giving Lysa a poison to kill him.
Arya mentions that Beric Dondarrion was temporarily on her hit list.
Jon and Ghost's reunion is similar to their reunion in "First of His Name".