Plot hole: In the second Shrek movie, we find out that Fairy Godmother and the King had a deal that Prince Charming would save Princess Fiona from the keep, hence becoming her true love and breaking the curse. In the fourth movie, we start with Rumple monologuing about how he almost had the Kingdom by signing a deal with the King. Why would the King be so desperate to try and reverse the curse by signing a deal when he knows he has a prior attempt through Prince Charming, assuming it would take the same time for the messenger to return with news about Charming and Fiona either way?
Suggested correction: It is stated in the intro that when "days turned into years" of waiting for a Prince to rescue Princess Fiona, the king and queen resorted to more desperate measures - enter Rumpelstiltskin.
Plot hole: When Astrid gets on Toothless for the first time, Toothless takes off uncontrollably and tries to scare her. Hiccup seems to have no control over him at this time. How is that so if with the new tail fin, Toothless cannot fly without Hiccup's precise control of the tail fin? That whole sequence would have fallen apart. This mistake was even admitted to on the DVD commentary. (00:53:35)
Plot hole: Near the end of the film, Carrie gets a quarter pipe. The problem is that there is no pavement anywhere near the farm which was expressed explicitly earlier in the film. Because of this, she won't be able to use the quarter pipe anyway, especially since it is about 2 ft at the base so they would definitely need to build the rest of the ramp. (01:14:00)
