What is an episode of a show that seems like filler, but ends up having major plot significance later on?

Submitted ⁨⁨2⁩ ⁨months⁩ ago⁩ by ⁨bOt@zerobytes.monster⁩ to ⁨television@zerobytes.monster⁩

https://www.reddit.com/r/television/comments/1vji3aq/what_is_an_episode_of_a_show_that_seems_like/