Fletcher's hand having a mind of it's own in the blue pen scene is pretty far-fetched, even for a film about a child's wish coming true. But it makes more sense when you realize Fletcher pretends his hand has come to life while he plays with Max all the time. The magic is completely mental, so it's using things his mind is already used to.
When Fletcher gets Samantha to admit that she lied about her age so she get married, he triumphantly shouts "AND THE TRUTH WILL SET YOU FREE!" at the top of his lungs. When you think about this a minute, you realize that's actually a fairly accurate description of what follows: However legally dubious it might be in Real Life, in the context of the movie, the truth set Samantha free from her contract.
This Troper always thought Audrey's boyfriend bared some slight resemblance to Fletcher, even having some of the same facial expressions. At first I thought that was odd.... until I realized that might have been deliberate. Audrey got driven away from Fletcher.... only to start dating a guy who looks like him.
A lot of people do tend to do this in real life, and not just with people who resemble their exes.
I used to think that when Fletcher found out that his son wished he could be incapable of lying for 24 hours, they why couldn't Fletcher unwish it. The reason Fletcher couldn't do it himself because 1st: It was Max's wish and 2nd: it was a birthday wish.
Fletcher gets to reunite with Max at the end but he does so by ruining several dozen people's travel plans.
There's a very real chance that Max learned the wrong lesson from the events of the film and lied about using his second birthday wish to for a pair of rollerblades, instead secretly wishing for his parents to get back together after all.
Fletcher is able to say things he believes are lies, but are actually true (as seen in the scene where he convinces the judge to recess for a bathroom break by describing the health impacts of holding it in). Ergo, shouldn't he be able to tell the validity of any statement simply by attempting to speak it aloud?
No, he says "I've heard that", which makes it a statement of hearsay or something, instead of absolute truth.