I'm not sure about jet engines, but a "wet start" is when you allow fuel to pool a moment before igniting it. Makes a nice Bang.

In this case, most likely the pilot would pool kerosene within the engine and then ignite, causing a helluva exhaust plume. I am guessing here.

I imagine the prank could be dangerous. I don't know if it's practiced these days, but I have heard of it happening on carriers.

Most likely in these times, doing it would get the pilot drummed up.