1 {scene: An airfield tarmac. Haken and Erwin are marching Ginny and the Joneses across it at gunpoint.}
1 Erwin: So now we take you to Berlin by zeppelin.
1 Haken: Ja. You tell them, Erwin.
2 {silent beat}
3 Erwin: {to Haken} Shouldn't we be saying something funny now?
3 Haken: Nazi science sneers at punchlines!
4 Monty: What are you two talking about?
4 Haken: Nazi science sneers also at die fourth wall!

You got this fourth wall gag because I couldn't think of anything else funny to go in between the Nazis capturing the archaeologists and them being on the zeppelin. I get severely stuck with writer's block sometimes.

That's the Graf Zeppelin by the way. The photo is from an old postcard showing it moored in Los Angeles.

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2015-05-26 Rerun commentary: Panel 3 shows a good example of "face the audience", or the social semi-circle. Usually characters in this comic are shown not directly facing one another when they are talking, so that the camera can have an angle which shows both of their faces at once.

It's one of those bits of stage blocking which you have to learn when composing a view for a comic frame (or analogously for a movie or video) - whether you draw it or photograph it. Usually the aim is to make it subtle enough or standard enough that the audience doesn't notice it. But in this case it looks particularly odd.