It could be that the man got in their way or didn't follow their instructions. Sometimes in cartoons, the reasons for such reactions can be quite simple and straightforward.
It could be that he's trying to get someone's attention or express his frustration. Sometimes, characters in cartoons yell for all sorts of reasons related to the plot or to create drama.
The woman might be yelling at the man because he broke a promise or did something that was unexpected and upsetting. Cartoons often use such scenes to create drama and entertainment.
It could be that the old man is expressing anger at some injustice or unfair situation he perceives. Or perhaps he's lost his mind and is just acting out randomly.
It could be that Peter's immaturity showed in a crucial situation. He might have been over - confident and tried something really risky without thinking it through. The Avengers, being more experienced, would be frustrated with his recklessness and thus yell at him. They want him to learn and grow, but his actions might have been too much to tolerate at that moment.
The reason could be various. It might be for relaxation, to socialize, or even because it's a tradition in the cartoon's setting.
Parents yelling in cartoons can be for various reasons. Maybe the kids are in danger and the parents are panicking. Or it could be to show that the parents are stressed and not handling the situation well. It's a common plot device to make the story more interesting.
Stress and danger can also be reasons. When facing a powerful dark wizard or a difficult situation at Hogwarts, the pressure can get to them. Harry may yell out of frustration at not being able to find a solution quickly, and Hermione might yell back as she tries to keep him calm and rational. In a fanfic, this can create a lot of emotional turmoil and keep the readers engaged.
Well, it could be because the kids did something wrong and the parents are trying to discipline them. Or it might be used to emphasize a point or add some excitement to the cartoon plot.
Sometimes moms in cartoons yell because the kids are misbehaving or not listening.
Parents might yell in cartoons to show their frustration or to try to discipline the kids quickly.