Rob and Kev switch on the holographic blind on their Breen loading dock to discuss "Mirrors", which turned out not to be quite the contribution to Mirror Universe lore they were expecting. To make up for it, they revisit all the other appearances of the Mirror Universe, including "Mirror, Mirror" (TOS), "Crossover" (DS9), "Through the Looking Glass" (DS9), "Shattered Mirror" (DS9), "Resurrection" (DS9), "The Emperor's New Cloak" (DS9), and "In a Mirror, Darkly, Parts I & II" (ENT). They also briefly reflect (!) on Discovery's sojourn in the Mirror Universe in season one of that show.
DIS 5×05 Mirrors
The Original Series
TOS 2×10 Mirror, Mirror
See also Subspace Radio #4: Remembering Nichelle Nichols
Deep Space Nine
DS9 2×23 Crossover
DS9 3×19 Through the Looking Glass
DS9 4×20 Shattered Mirror
DS9 6×08 Resurrection
DS9 7×12 The Emperor’s New Cloak
Enterprise
ENT 4×18-19 In a Mirror, Darkly & In a Mirror, Darkly, Part II
TOS 3×09 The Tholian Web
Discovery
DIS 1×10 Despite Yourself
DIS 1×11 The Wolf Inside
DIS 1×12 Vaulting Ambition
DIS 1x13 What’s Past Is Prologue