wizard hat: n.

[also, after Terry Pratchett, pointy hat] Notional headgear worn by whoever is the wizard in a particular context. The implication is that it's a transferable role. “Talk to Alice, she's wearing the TCP/IP wizard hat while Bob is on vacation.” This metaphor is sufficiently live that one may actually see hackers miming the act of putting on, taking off, or transferring a phantom hat. See also pointy hat, compare patch pumpkin.