My family stayed at my house and “the TV wasn’t working,” because it doesn’t have network access and I use an Nvidia Shield instead, so they connected it to the Wi-Fi and ad overlays showed up in the menus! I’m still mad about it years later.

Luckily I dodged a bullet and it didn’t brick it or anything, and the ads went away when the internet access did. I just disconnected it from the network and manually banned the MAC address in case anyone else tries it again.