1 Head Death: Now, Sat On By A Giant Frog, I received a memo from War, saying you borrowed his giant frog.
2 Head Death: This violates jurisdictional separation of the four Departments of the Apocalypse!
3 Head Death: We can't have War mongering giant frogs everywhere!
4 Death of Choking On A Giant Frog: It'd make for a ribbiting conflict...
4 Head Death: What was that, Choking?
4 Death of Choking On A Giant Frog: Nothing...

2012-11-16 Rerun commentary: This strip uses the old word "mongering", in the sense of "dealing in a commodity", like a fishmonger deals in fish. So the sentence can be read as "We can't have War (one of the Horsemen of the Apocalypse) selling/trading giant frogs everywhere!" This is the literal meaning of Head Death's sentence.

Of course the pun is that "War" plus "mongering" produces the completely different meaning slipping into the middle of the sentence - "warmongering" - which can be read as an adjective modifier in front of "giant frogs", viz: "We can't have warmongering giant frogs everywhere!"

Panel 4 is really just a topper.