You know...with YouTube being so prevalent, I'm surprised that parents would fib to their kids about a ride.
We have been watching YouTube ride through videos of all the rides my son is tall enough to go on come our December trip. We've also been watching a Disney Special on Netflix every week so he sees (some of) the rides and is prepared for when we get to Disneyland to say "yeah, I'll ride it" or "no...I remember this one from netflix/youtube and I'm not ready for it". Now, do I expect him to ride the few things he's told me he WANTS to ride based on seeing it on Netflix or YouTube...nope. I'm prepared to be cool with his decision and I won't push him to go on something he doesn't want to go on. Nothing worse (in my opinion) than scaring the crap out of your kid and having a miserable trip because they won't get on anything other than Dumbo or Pooh.
We do this too. DS was excited to be tall enough to ride some of the rides, but after seeing some of the videos he has decided to wait a little longer to ride them.