Probably a couple of ways - Bluetooth and you accepted his connection - If he was ever in your house and asked for WiFi password and your tv is on the same WiFi he could connect without you approving anything. Back when that technology was starting out we were on stag in Manchester. One of the lads had gotten the password for WiFi from barmaid earlier in the day. Later on United were playing on the big screen TV and he noticed he could connect to the TV. He flipped on Timbos Goals with Gerrard goal against United At Anfield in 01 on his phone and then put it on the big screen in the middle of match. He didn’t even let onto us. The place was packed, he kept his composure and only told us after we left as would have got a serious hiding had he been outed. Seen something similar in Galway one year at the races when someone put on porn on the TVs in the Quays pub.