In an alternate timeline, somepony else got to the Mirror Portal before Sunset and stole both it and Celestia away. Acting Princess Cadance is willing to give Sunset a second chance, and hopes to have Sunset's help with a matter of national security.
Sunny Flare gets her first report card of Principal Cadance's tenure, and it's not good. Her mother, former-Principal Abacus Cinch, has an uncomfortable explanation for that.
Three Shadowbolts on the eve of graduation start a podcast about magical disasters – a conceptual crossover with Well There's Your Problem, a podcast about engineering disasters.