Science Marches On: Originally, Paradise Island was kept hidden from the world by being always covered by clouds. When satellite mapping was invented, someone would have noticed that one spot of the ocean was always cloud covered and would have investigated. So it was changed to magic somehow keeping it hidden.
Doing It for the Art: Carter sometimes did her own stunts because it allowed better closeups of the action. In one memorable scene she hung from the bottom of a helicopter as it took off; she later stated that the producers were... less than pleased when they found out.
Keep Circulating the Tapes: The first TV pilot movie, starring Cathy Lee Crosby and Ricardo Montalban (as the bad guy), is mostly forgotten today. It was once released on VHS, and didn't make it to DVD until 2012.
What Could Have Been: Wonder Woman's swimming costume was originally a bikini, but the one that was designed had trouble staying on in the water (oh, to see some test footage of that...), so they redid it as a full-body outfit.
Debra Winger was supposed to appear in more episodes, and there was even talk of a Wonder Girl spinoff, but she wanted to focus on more dramatic work.