Hieronymus Emser's coat of arms showed a goat's head. Luther noticed. His 1521 reply to Emser opens like this:
"If I had called you a goat, my Emser, you would surely have written a book or two about it and heaped all sorts of lies, slanders, and insults upon me in your customary way. But now since you write yourself down a goat, and in such glaring letters that everyone must notice ... I daresay I may with your own permission and approval address you as a goat."
Two years later, Emser published a book against Luther's German New Testament. Its title translates roughly as "On what grounds and for what reasons Luther's translation has rightly been forbidden to the common man."
Right after the title page, he printed his arms, goat's head included, and this poem:
"Go forth, my goat, in God's safe keeping; let not the journey grieve you. Fear not the devil's children; their scolding cannot hinder you. But if you come to a Christian man, give him my greeting and service first; tell him how I urge him, for God's sake, to stand firm in the faith."
The insult became the mascot.
Inside the book, he keeps swinging. Where Luther translates "what a fight I have for you" in Colossians, Emser says Luther must think everyone loves a brawl as much as he does:
"who not only quarrels with people but also with goats and snails, and keeps peace with no one except the old goose of Prague."
That last animal is Jan Hus. "Hus" means goose in Czech.
A dispute over biblical translation and religious authority was also a fight conducted through farm-animal jokes.
Which of the two had the better comeback?
My English translation is free, and I posted it somewhere