Let it never be said that Marvel's Agents of S.H.I.E.L.D. doesn't know how to celebrate an anniversary! The show's 100th episode pulled out all the stops, revisiting old storylines and characters going all the way back to the pilot. It even delivered the wedding we've been dying to see for five years — with a huge twist.

Thanks to the explosion that blew up the three dangerous monoliths stored in the base at the end of last episode, a world-ending event was put in motion. The destruction of the stones created a rift in space-time, opening a gateway to what Fitz (Iain De Caestecker) dubbed the "Fear Dimension." Basically, all the team's worst fears came out to play, allowing for familiar faces — both friends and foes — to return.

Lash, Hive, and even a few roaches appeared to wreak havoc, as did a Kree warrior, a murderous LMD, and, in a more existential sense, the great outdoors. Deke (Jeff Ward), you precious, agoraphobic little dork!

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The best visit of the night, however, came from Mike Peterson (J. August Richards), a powered man and eventual S.H.I.E.L.D. agent we met in the pilot.

He first appeared as yet another manifestation of the Fear Dimension, claiming to be a hallucination of Coulson's (Clark Gregg) mind. As he told it, Coulson was still on the operating table after being stabbed by Loki (Tom Hiddleston) in the first Avengers film, desperately clinging to life. According to him, the last few years had just been the random firing of synapses in Coulson's brain as his life slowly ebbed away; the last, desperate attempt of his dying mind to tell a story where he lived out his days and saved the world on a regular basis.

Even though it was obviously a lie, that notion festered in Coulson's mind. What if none of this had been real at all? What if his mind made up students to teach, a partner to pine for, and a daughter to guide through the world as a way to give him one last hurrah?

Luckily, the real Mike Peterson showed up to blow that hallucination away and help Coulson close the rift. Phew!

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With the crisis averted, Fitz and Simmons (Elizabeth Henstridge) decided they didn't want to wait one more day to exchange their vows and start their life as a married couple. In a beautiful lakeside service, FitzSimmons finally earned their nickname by becoming one. Awwww!

It wouldn't be Marvel's Agents of S.H.I.E.L.D. without a twist though. Deke had ventured out into the world to gather all the necessary items like a wedding dress, booze and the rings, and he mused that he picked Jemma's because it looked just like his grandmother's ring that his mom wore. As if that wasn't obvious enough, General Hale (Catherine Dent) later confirmed that his DNA test matched both Jemma and Fitz, making him their grandson!

We're going to need them all to figure that out ASAP because can you just imagine the look on Fitz's face when he realizes Deke's his descendant? Too precious for words!

Marvel's Agents of S.H.I.E.L.D. airs Fridays at 10/9c on ABC

Jeff Ward, <em>Marvel's Agents of S.H.I.E.L.D.</em>Jeff Ward, Marvel's Agents of S.H.I.E.L.D.