MARTY’S ORLIN showed up because he promised Allison he would. Also he’s been feeling rather lonely and isolated since Elsa’s disappearance. He needs to get back to socializing so he doesn’t spend all of his time in the clinic. He’ll be making awkward conversation with anyone who looks his way.
OBI-WAN showed up and helped with the decorating. He figured this was a good opportunity to get to know people and learn the truth about Derleth.
SPOCK did not attend. He spent the day going over Mobius’s research in the lab.