The first one that I thought of was Once We Were Gods (Season 3, Episode 15.)
We get so many good interactions this episode!!! My favourites have to be the scene between Alexander and Nick in the car, and the one between Adalind and Meisner in the cabin.
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Other episodes that come to mind are:
Last Grimm Standing – This is probably my most watched episode (hell, I wrote a fic inspired by it after I watched it – which can be found on my wattpad). This episode has my favourite Nick and Monroe content (i mean if you don’t fight for you friend’s life are you really a friend?)
Beeware – This is a comfort episode of mine. I really like the mellifers, wish we’d gotten more of them.
Where The Wild Things Were – I am a bitter Juliette/Nick shipper, and I really do like the episode and the closure it gives them.
Stories we Tell our Young – This one has the scene with Nick and Alexander, after he’s been arrested, and that’s one of my favourites. I think about it a lot. The messsage of the episode is good, to.