1 Isaac Newton: The plan shall be as follows: You distract the Pope, I'll grab Galileo.
2 Edmond Halley: I doubt a better plan has ever been formulated. But how shall I distract the Pope?
3 Isaac Newton: I don't know. Stand in front of him and sin, or something.
4 Edmond Halley: I can act Protestant. Will that do?

I initially wrote Halley's punchline as, "I can be Protestant, will that do?"

But unfortunately that doesn't accord with historical reality, for Edmond Halley was in fact an atheist, and well-known for being so. In fact, despite Halley helping Isaac Newton (a staunch Christian, although with highly unorthodox interpretations of scripture and Christian theology) get his masterwork Principia Mathematica published in 1687, Newton supported the rival David Gregory over Halley for the post of Savilian Professor of Astronomy at Oxford University in 1691, based primarily on Gregory's more palatable religious beliefs.

And, in these times, being a mere atheist was less offensive to the Roman Catholic establishment than being a Protestant, so having Halley declare, "I can be atheist, will that do?" just wouldn't have the same punch. So in the end I settled for having Halley act Protestant, and thereby being maximally offensive to the Pope.

Given how historically accurate the rest of this strip is, I feel good that I got this detail sorted out properly.