I loved Happy Days. Fonzie was my favorite character, and I still use his catchphrase "Sit on it." When I saw the now legendary "Jump the Shark" episode, I thought it was awesome. True, I was eight at the time, and maybe I didn't understand that the writers were struggling with where to go with the series, but I saw nothing wrong with a guy wearing a black leather jacket jumping his motorcycle over a shark.
Okay, now I kind of see what people made such a fuss about. It's trite, contrived, and just plain silly. But being a NaNoWriMo participant, I get it. That's because NaNo allows you to jump the shark without worry of ridicule. If you're stuck in the story, unsure where to go, it's fine to "jump the shark" by killing off your main character or having them doing something totally outrageous things to get to the next chapter. Unlike the writers of Happy Days , you can always fix it later.
In my current NaNo novel, I've managed to switch protagonist completely because I got bored with mine. The story began in 1596 England and is now currently taking place in present day Louisiana. I started out with magic mirrors and ended up with voodoo priestesses who like to fool around with Greek gods.
How will the story end? Does it matter? Nah. Not to me anyway. NaNo is one long writing exercise with multiple opportunities to try things you might not normally do in telling a story. The only thing that really matters is reaching the finishing line with your 50,000 words.
So I say, "Jump that shark, baby."
Have fun doing it!