Penguins have dominated recent nature films and cartoons, so it was probably only a matter of time before they loomed large in national tests.
About 600,000 pupils in primary schools buckled down this week to answer key stage 2 test questions on subjects including penguins, cleaning fish tanks with magnets, and getting babies to sleep.
On Monday, pupils sat the science paper - traditionally the test in which they do best. But some were confused by a question asking them what feature penguins had. Their answers included "fur".
The annual Sats discussion on the TES online staffroom forum was soon buzzing with complaints about the "infamous penguin question". One teacher wrote: "I am beginning to regret showing my class the April 1 BBC prank video about the flying penguins."
Another question that irritated teachers asked what could scientists measure or observe to find out how well babies slept.
One pupil proposed looking to see whether the baby was snoring. Another answered: "Mummy says my brother never sleeps and she is losing it."
The question was particularly pertinent to Donna Thomas, a Year 6 teacher at North Mundham Primary School in Chichester, West Sussex. She was there to supervise her class, despite having had a baby girl seven weeks ago.
"It was not the best question on the science paper because it was about using a bit of common sense rather than testing curriculum knowledge," she said. "But it said babies sleep better if they have more daylight, so I'm now taking mine outside to play."
Questions in Tuesday's writing paper included writing the biography of an imaginary 19th-century man who invented fairground rides. Wednesday's reading test was on weather, and the maths tests were due to end today.
Secondary teachers were critical of some aspects of the previous week's KS3 tests, mainly focusing on the Shakespeare paper in the English exam.
A question on Much Ado About Nothing asked: "How do these extracts explore the idea that loving someone is not easy?"
One teacher wrote: "What do they imagine the answer to be - 'It is difficult falling in love because you might do so at the exact point that your new girlfriend wants you to murder someone in an honour killing'? That's always happening to me."
PUPILS' ANSWERS BRING COLD COMFORT
Q: What feature do penguins have?
A: "They're funny."
Q: How does this help them survive in their environment?
A: "They keep their friends amused so they like them."
Q: The parents must be careful that the sunlight does not burn the baby. Describe one way parents can keep babies safe in sunlight.
A: "Put a plastic bag over it."