Can a catholic receive communion in Greek orthodox church?

Oh, dude, technically speaking, it's a bit of a gray area. Like, in general, the Greek Orthodox Church has guidelines about who can receive communion, and typically, they prefer you to be a member of their church. So, like, if you're a Catholic popping in for a visit, they might not be too keen on you joining in on the communion party. But hey, if you're really craving that Eucharist, maybe give them a heads up and see what they say.