I am fascinated by medieval Christian depictions of Biblical events with obscene marginalia. Like this page depicting Christ carrying the cross & a man shooting an arrow at another man's bare butt.

[TW: nudity & poop in thread]

(Morgan Lib, MS m88, f. 176v) #MedievalTwitter

Or this depiction of John the Evangelist writing the Gospel of John, while a monkey squats in the margin and poops.

(Morgan Library, MS M28, f. 013r) #MedievalTwitter

It sometimes happens in historical texts, like this sober page from a history depicting the Defeat of Cadwal, while a hedgehog watches a monkey shit.

(BL, MS Royal 15 E IV, f. 180)

Or this depiction of the Holy Spirit descending to the Virgin Mary and the Apostle Peter, while a man in the margins has a snake biting his groin.

(Morgan Library, MS m729, f. 273r)

The ones that REALLY fascinate me are where the artist seems to integrate the obscenity into the image, as here, where Peter the Apostle looks up towards the Holy Dove descending towards him....& just past it, a monkey exposes its anus at him.

(Morgan Lib, m754, f. 009r)

Another page from the same manuscript, where the same thing happens to the Apostle James, who sees the Holy Dove and, just beyond it, another monkey anus.

(Morgan Library, MS m754, f. 015v)