1 Qui-Gon Jinn: There’s always a bigger fish.
2 Jar Jar: Muy muy, but howsa can that besa?
3 Jar Jar: Thissa means there’sa no biggest fish. But wesa observe a fish, so bysa inductions theresa must besa an infinite sequenca of progressively largersa fish.
4 Jar Jar: Thissa implies the whole universe issa fish!
4 Qui-Gon Jinn: It’s just a wise-ass saying, okay!

I originally wrote this with Jar Jar's line in panel 3 as follows:

Jar Jar: Thissa means there'sa no finite biggest fish. But wesa observe a fish, so bysa inductions theresa must besa an infinitely large fish.

I showed some of my friends, and this conversation ensued:

Friend 1: It doesn't imply there's an "infinitely large fish", that wouldn't even help. There's just infinitely many sizes of fish.
Friend 2: I'm afraid Jar Jar's reasoning has led him astray.
Friend 1: Can't have Jar Jar getting it wrong; it'll damage his reputation as a genius. It would imply the ocean is infinitely large though.
Friend 2: Not if infinitely many of the fish are nested.
Friend 1: I don't see how nesting helps. Any finite ocean is too small for one of the fish. Oh wait I get you.
Friend 2: All but a finite number of fish are in a matryoshka fish-chain.
Friend 1: You mean the fish are like, "5 - 1/n" or something? There's still infinitely many of them above a finite size though. Oh, but you're putting them all inside each other then, okay.
Friend 2: Obviously this poses philosophical questions as to what fish even are, if they can nest. Nonetheless!
Friend 1: You end up with arbitrarily thin fish. I'd say it wouldn't work in practice, but, well...
Friend 2: Then we apply inverse Banach-Tarski...
Friend 1: A fish can't be bigger without being measurable. We're talking about the real world here not some fantasy axiom-of-choice abiding universe.
Friend 2: Axiom-of-plaice. Hmm. If I have a non-measurable thing N, and I add something to it, do I not end up with a still-non-measurable-but-larger thing?
Friend 1: No, you probably end up with something exactly the same size.
Friend 2: That makes sense.
Friend 1: You could define "larger" to be "a superset of", but you have to settle for being unable to compare the size of most things.
Friend 1: So.... to fix the joke, maybe: "Thissa means there'sa no biggest fish. But wesa observe a fish, so bysa inductions theresa must besa an infinite sequenca of progressively largersa fish." (and punchline unchanged)
Friend 2: Harrison Ford: Kid, it ain't that kind of comic.

So thanks to my friends for being the sort of nerds who help me fix jokes like this.