Students who didn't read all of their teacher's instructions were caught red-handed when he added a cheeky instruction to their homework.
Tyler Jackowski, a teacher, from Boston, US, on TikTok, explained that he uses the method to keep his students "on their toes."
And it left people in stitches - with some viewers admitting they wouldn't have passed the test.
His video has been viewed nearly 2.4 million times since being shared on TikTok.
He said: "When I'm making study guides for my students, sometimes I like to keep them on their toes.
"So I'll write things like 'tell Mr J he smells bad in the chat."
The teacher then cut to a clip of himself at the computer, while a cheeky pupil follows his order.
He replied in a deadpan manner: "That's really rude," and joked in the caption: "Enjoy detention."
The video racked up nearly 400,000 likes - and viewers were in hysterics by his addition to the study guide.
One joked: "You clearly said 'in the chat' and she said it out loud, didn't read the instructions SMH."
Another teacher admitted: "I make one question on every test 'Who is your favourite teacher?' and I make it multiple choice and every single choice is me."
A third commented: "It is an effective way to make sure they study."
Another student said: "I have a prof who writes "Tell me I look nice and get extra credit,'
"She does it too, she says it works for her to know who reads the instructions."
One fan added: "Awwww, you're a teacher who will be remembered."
Meanwhile, a mum-of-one went viral after criticising bedtimes and describing cribs as "little baby jail cells."
Mum Alice Bender, of Arizona, sparked a huge debate online after sharing her parenting techniques in a viral TikTok.
The video by comingupfern describing how she is raising her five-month-old Fern has racked up more than 7.6 million views since being uploaded to TikTok.
In it, she explained why she doesn't use a crib for her son to sleep in.
What do you think of the parent's technique? Let us know in the comments below.
