The Essex lovebirds embraced their neon fancy dress for the cast party, which was being filmed at Chelmsford in Essex.
Fran and Diags donned bright outfits and fancy face paint for the occasion, with the pair sharing a smooch in the middle of the dance floor. Aww, they look so loved-up!
And check out Diags' fibre optic lights on his head!
Earlier in the day, Fran and Diags shared a smiley selfie as they took a break from the party, which was also attended by the likes of Charlie Sims, girlfriend Ferne McCann, Jasmin Walia and new cast member Dan Edgar.
This week, Fran marked a full year on the ITVBe reality show, where she told fans she was grateful to be casted as it bought her and Diags together.
She tweeted: "Wow a whole year since I've been with @OnlyWayIsEssex, what a crazy one but, if it wasn't for TOWIE, I wouldn't have been with my soulmate."
And, after last night's show, fans asked to see more of Fran on their screens.
She assured them that she would be appearing on Sunday's episode, adding: "I got no drama babes. Quite enjoying it to be honest."
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What were Diags and Fran up to in series 13? Recap here!