I watched "New Leaf" again. I think I liked it better the second time (a couple jokes I missed the first run-through.) It's one of those episodes where Spongebob has almost no lines; the majority of the episode is focused on Mr. Krabs and Plankton.
Can't recall the writers, but I'm pretty sure it's many of the writers we've seen in some of the more recent season 4 episodes (some combo of Steven Banks, Luke Brookhiser, Eric Wiese, Tom King, Chris Mitchell, Casey Alexander.) I'm pretty sure Paul Tibbitt wasn't one of the writers, I'm pretty sure I would remember that since he's one of the few writers from seasons 1-3 who still writes.