Walter has two sons

That week, Walter's wife Rebecca was on a business trip in China. So he resorted to test it with his two sons.

Peter was 18 and was in the last class of school. He's the shyest of the two and hasn't had a girlfriend yet.

Then there was Jacob. Jacob was 24 and almost the complete opposite of Walter. They shared the same hair and eyes, but Jacob was overweight and somewhat of a weakling.

On this rainy Saturday afternoon they both heard their father's voice scream "Hey guys, I have to show you something fantastic!".
Unfortunately, he caught both of them in a bad moment while they were masturbating...

Almost half an hour later, both stood in front of him in his basement workshop / laboratory.

"There you are at last!" they heard his booming voice. "So, just so you all know, I have invented something and you may not see me for a while!".

"What are you testing?" Jacob added.

"Look, it's hard to explain, and it doesn't really matter. I just need you to trust that I need to go for a while, but I will be back."

"No, that's not good enough! I need to know why." Jacob insisted.

"Fine. I'm testing a device that allows me to transform into other people. I know it works, but I need to make sure it lasts, that it will work for a long time." Walter explained, now slightly annoyed.

"Bullshit." Jacob went on.

"You don't believe me? Fine. I'll prove it to you." Walter responded.