1. historically, a fishing boat that would fish for pickled herring would come in to dock last. so "coming in off the pickle boat" or "falling off the pickle boat" would mean that you're the last to find something out, and would like an ass for saying it.
2. alternate definition: a cock that's bent in a downward angle when hard.
Q: "Did you know that OJ killed Nicole?"
A: "Dude, I didn't just fall off the pickle boat you know."
Q: "Yo Keith, why your ass bleedin' so bad?"
A: "Huh? Wha? Yeesh, I just fell off the pickle boat!"