To pull a "kasai" is to show up suddenly (either in real life or
on social media), say Hi, and then quickly leave/
disappear without a trace. Often times interrupting a conversation two others may have been having.
Person 1: So have you seen that new movie about
Eagles?
Person 2:Oh yeah that was pretty great my favorite part was whe-
Person 3 shows up
Person 3: Hi
Person 3 leaves
Person 2:
Fucking bastard pulled a kasai.