OOC - Missy's Barry was there to celebrate with Cath and Jest. He was the one who welcomed the Jester to their world, and was excited to support their wedding. He hung around with Evan a good deal of the time, and only pouted a little when Evan had to go back to work after.
Sharon was there, too. While she has an office, she practically keeps office hours at Sally's.
Henry showed up for a little while to celebrate and snag some cake, but then had to head back to work himself. Being the Science Team's second in command meant that he didn't have too much time to offer, though he spent as much of it with Kaylee as he could (if she was there).
Of course Thor was there, as he was the officiant of the wedding. Zari wrote up basically everything he was supposed to say, and things only got a little awkward (and incredibly charming) when he went off script. After a couple of death glares from Zari, he probably stuck to the script for the rest of the ceremony. And he's available for dances at the reception.
Steve stayed pinned to Derek's side, and left the reception with him so they could head back to their place together for the moon.
While Kate wasn't really interested in all things love and happy at the moment, she was all about all things cake. A frequent visitor of Sally's, she knew how amazing both the food and coffee were, so she knew it would be to die for at the wedding. So she showed up, hugged Clint, tried not to feel as miserable as she really felt, and then headed home. She had dogs to take care of at the ship, anyway--let Kaylee stay and dance with Henry.
Yelena sought out her loved ones (Eliot, Natasha, Clint, Clark, ...Kate...) to spend time with during the ceremony and reception.
Lydia dragged Allison out to the wedding so they could dress fancy and get some dancing in. They probably reached out to Malia to go with them? Maybe? Though definitely needed some snuggly dancing time just the two of them.
And of course Cath was there. She was overwhelmed by the people and support and love and joy. She didn't let go of Jest's hand the entire time.