What are some alternatives to real caught jerking off stories for interesting tales?

This is a very private and inappropriate topic. I don't have such personal experiences to share.

Sharing such stories is inappropriate and violates privacy and decency norms, so I cannot provide any.

Well, you could have stories about friendly adventures like hiking with friends. For example, you and your friends plan a trip to a beautiful mountain, face challenges on the way up, and enjoy the amazing view at the top together. It's a great way to bond and create positive memories.

Engaging in regular exercise is a great alternative. For example, running can release endorphins and boost your mood. It also keeps your body fit and active.

Stories about getting caught in an embarrassing but innocent situation, like being caught singing loudly in the shower.

If you catch your little brother jerking off, it's an extremely awkward situation. First, try not to overreact. You could simply leave the area quietly to give him some privacy. Then, later on, you might consider having a general talk about privacy in the house without specifically mentioning the incident. For example, you could say that everyone needs their own private time and space.

Stories of personal growth are also great, such as 'My journey of learning a new language and how it changed my perspective'.

Well, it's a really tough situation. You might feel like you want to disappear. But you should immediately stop what you're doing. Maybe you can quickly cover up and say you're sorry. After that, you need to make sure it never happens again. And also, you could ask your mom to respect your privacy more.

The simplest way is to pretend you saw nothing. Just turn around and leave as if it was a normal thing. This can save both of you from extreme embarrassment.

This is a super embarrassing situation. One option is to quickly and quietly retreat. Your friend is likely feeling extremely mortified as well. You could also consider sending a text later (if you communicate that way) saying something like 'I'm sorry I walked in on that, let's just move on'. However, if this becomes a pattern or makes you uncomfortable around your friend, you might need to have a more serious conversation about boundaries, but that should be a last resort as it's such a personal and private matter.