There is another out-of-ordinary sample in Phineas and Ferb. When the kids travels to the future, adult Candece, who hasn't got over it, steals their time machine, travels back in time to the first time and pulls her mom out to show her what the kids has done. Then back in her present, she finds out that her action has dramatically altered the future. So she travels back in time again to stop the previous herself to change the future.
Could someone edit the Angel example for chatter? It has spoilers so I can't do it as I haven't seen the final season.
Also, I'd ask whether or not to remove the Merlin example altogether - it doesn't fit the trope to me, but what do you think?
"Hercules: the Legendary Journeys." The first few episodes are in the form of mini-movies, and both Hercules and Iolas get married and have children. When the series proper begins, Hercules' family are killed, so they have an excuse for disappearing, but Iolas' family just sort of evaporates and are never heard from again.
How is there a reset button in Small Gods? Over the course of the book the Omnian religion is changed completely. Subsequent books featuring Omnians all use the changed version. Nothing gets reset. Likewise "the whole Koom Valley Thing"; the battle of Koom Valley may have happened several times, possibly owing to temporal manipulation, but it stayed happened every time.
I'm not sure about Johnny and the Bomb either. Things are changed, and they stay changed. Whether characters remember that they used to be different is completely irrelevent.
Edited by DaibhidC