Lost in Space and Happy Days really confuse me...
They were just random guesses.
Unless I'm getting it confused with Star Trek, I thought there were episodes of Lost In Space where they went to alternative Earths only to find out they were evil traps of some kind? Probably I'm wrong. Only saw both shows when I was a kid. (Yeah, I was a Star Wars kid and never liked Star Trek much. Plus they didn't air it much in Australia. Still don't by the looks of it.)
As for Happy Days: I glanced at the picture while at work without zooming and misread the boy's face as a young Richie and the other child as Joanie because of the hairstyle. I thought it might be some bizarre episode where they went on holiday or a dream sequence of something. Didn't really think it was correct. I was actually going to guess The Hardy Boys next but by then The Famous Five had been guessed and I suspected it was correct because of the more British-looking settings.
Plus, people often post up pictures on purpose that are misleading in setting, or otherwise, as a diversion.
By the way, you said video quality was so different. Apart from Cassie saying sorry for the quality of the shots, which could have meant the actual show had better quality IRL, you guessed from the quality that the show was from the 70s:
"Happy Days is an American television sitcom that aired first-run from January 15, 1974..."No real need to call people out for crazy guesses though is there? It could kind of make people feel like they are being told they are wasting everyone's time in a thread that's just for fun anyway, right?

(Oh, and I don't mean specifically you, VampireWombat. It happens quite a bit in this thread. Maybe if we didn't do that newer AGS members would feel more comfortable to have a try instead of just the regulars who already feel pretty secure here in the forums?)