OMG. You live with 2 GenZers. You deserve a medal or something. I think any prank on them would have to involve their phone, and getting hold of it might be tricky. If I could, I'd add funny autocorrect replacements to their phone for commonly used words.

If not, I'd buy a cheap second phone in their vicinity and call it intermittently. They’ll be puzzled by the vibrating sounds coming from unknown places.

🤣