Panel 1: For some reason, we get an exterior shot of the plane as Emily thanks Mike for being a great help; he is uncharacteristically modest as he says that's okay.
Panel 2: We shift to the inside of the plane as he says that he's got a baby and ten year old sister at home. Since she doesn't know him, she says that they're lucky to have him.
Panel 3: She sets up the 'joke' by saying that she's sure they're thinking of him right now.
Panel 4: We then shift back to the Pattermanse so we can see Liz stare at a sign taped on his bedroom door: "go into my room, Lizardbreath and you are DEAD MEAT! Signed, the big M."
Summary: The sad thing is that Elly can also read that sign and not draw the correct conclusion: Mike is an ass to his sisters and needs correcting. She's distracted by other concerns, you see.