Eddie attempts to propose to Iris but is interrupted by the Reverse-Flash in episode 1x20 "The Trap".
Barry and Joe arrive at the location of another skin husk where Julian Albert is already investigating in episode 3x02 "Paradox".
The team arrives in the off limits year and finds the world filled with clones of Ava in episode 3x16 "I, Ava".
Liv sees Matthew Voss in a vision, and later she and Ravi find the scrapbook that was thrown away in episode 2x08 "The Hurt Stalker".
Etta takes Nina to see a newly de-ambered Walter in episode 4x19 "Letters of Transit".