Ep. 160: "In a Mirror, Darkly Part 1" (ENT S4E18)

For once, Ryan and Brady come not to damn Enterprise with faint
praise, but to celebrate it! This jaunt through the mirror
universe is easily the most fun they've ever had watching an
Enterprise episode, and they revel in the fun haircuts, the evil
dogs, and one of the simplest and most effective episode openers
in the history of the franchise.