aethelred
Explanation
The Joke
A portrait painter pleads with King Aethelred to please stop fidgeting so he can finish the royal portrait, warning that Aethelred needs to keep still. The king apparently cannot cooperate. A caption reads "months later," and we see the finished portrait -- which depicts Aethelred as a crude, ugly, distorted figure. The painter asks, "Can we do one more? Just five strokes? No? Goddammit."
The joke is that medieval royal portraits often look crude, stiff, or unflattering by modern standards, and the comic imagines a humorous in-universe explanation: it is not that the artists lacked skill, but that the subjects were impossible to work with. The king would not sit still, so the painter could only manage a rough, unappealing likeness.
The Humor
The humor comes from providing a fictional "behind the scenes" explanation for a real historical observation -- that many medieval portraits look oddly proportioned or unskilled compared to later periods of art. Rather than attributing this to the artistic conventions or technical limitations of the era, the comic blames it on the royal subject being a terrible model. The painter's exasperation adds to the comedy, as he is clearly a competent artist thwarted by an uncooperative king. The name "Aethelred" is itself inherently funny-sounding to modern ears, and likely references Aethelred the Unready, an Anglo-Saxon king of England whose epithet "the Unready" (meaning "poorly counseled") fits the joke perfectly -- he is literally not ready to sit for his portrait.
References
Aethelred the Unready (c. 966-1016) was King of England, known for his troubled reign during the Viking invasions. His nickname "the Unready" is an Old English pun on his name (Aethelred means "noble counsel," while "unraed" means "no counsel" or "poorly advised").