The cartoon boy could be asleep at the picnic because he exerted a lot of energy earlier and his body needed the rest. Maybe the weather was too warm and made him sleepy. Or, he might have had a long and busy week, and this was his chance to catch up on sleep.
Maybe he was just really tired from all the playing before the picnic. Or he could have had a late night the day before.
He could be asleep because it's his bedtime or he's worn out from playing too much.
Maybe he's just really tired and the hammock is a comfy place to catch some z's.
Maybe he's just really tired from playing all day.
Maybe he was really tired from playing and the tree provided a nice shady spot for him to rest.
It might be that the cartoon boy is sick or just exhausted from playing too hard. Another possibility is that the story is set at a time when it's naturally nap time for him.
Well, there could be various reasons. It might be that she's exhausted from playing or doing some activity. Or perhaps it's part of a magical spell or a plot twist to come.
Maybe the baby is just really tired and needs to rest. That's a common reason for babies to fall asleep.
The cartoon man might be asleep because he's recovering from an illness or because he's in a peaceful environment that makes him feel relaxed and sleepy.
It's possible that the environment is calm and comfortable, making the cartoon dog feel sleepy and fall asleep. Maybe it's also a way for the creators to add a touch of cuteness to the scene.