Maybe she's had a really long and tiring day and just couldn't hold her eyes open anymore.
It could be that he stayed up late the night before and is now catching up on sleep. Or perhaps the work he's doing is just so boring that it made him sleepy.
Maybe she's had a really long and tiring day at school or work and just couldn't stay awake any longer.
The kid could be sleeping on the desk because they stayed up late the night before. Or perhaps they find the classroom environment boring and dozed off. Either way, it adds an interesting element to the cartoon.
Maybe the kid was up late the night before and is really tired.
Maybe she's had a really long and tiring day at work and just couldn't keep her eyes open anymore.
It might imply a lack of inspiration or boredom. The man could be so uninspired by his work that he dozed off. Also, it could be a comical moment to lighten the mood of the cartoon.
The cartoon could depict the man snoring softly, with papers and pens scattered around the desk. Maybe there are some dream bubbles above his head showing funny or strange dreams. It might give a sense of exhaustion or a moment of needed rest.
The scene might show a tired woman with her head on the desk, perhaps surrounded by some papers or a computer. The lighting could be dim to give a sense of a late night or a long day at work.
He might be drawing or doing his homework.