Nope.
That's three guesses. So I'll reveal the answers. This question was tougher than I had intended it to be. o.O I like everyone's guesses. Clever, never would have thought of them. ^^
An ability gained, an ability lost
Answer: Spike
Explaination: While it is true that Spike speaks in LBT4 and seemingly never speaks again, this is not why this clue fits him, because he does indeed talk in a later sequel, in LBT8, when he shouts "MOMMA!" In LBT1, Spike is seen swimming in deep water with ease, no trouble at all. But in LBT8, we learn that he cannot swim and Spike is seen struggling to keep himself from sinking. From the span of LBT1 to LBT8, Spike had lost the ability to swim.
The clue was referring to an ability that was both gained and lost, not two seperate abilities.
Fight fire with fire
Answer: Ducky
Explaination: In LBT8, Ducky becomes angry with Spike, and becomes uncomfortable as the negative feeling starts to grow inside her. Misunderstanding Cera's advice, Ducky decides to get "pay back" by making Spike feel bad by staying angry at him.
The clue is a familiar phrase, although it does not neccessarily always mean a physical battle. Ducky was trying to invoke negative feelings on Spike (guilt) to relieve her own negative feelings (anger), using a negative feeling against a negative feeling.
Fear lies within
Answer: Cera
Explaination: Throughout the movie series, we have seen times when Cera is afraid, but pretends like she isn't, like in LBT1 when she pretends that she wasn't afraid when telling the tale of her encounter with Sharptooth underground. In the TV show, when the gang hunt for Hidden Runner, Cera attempts to hide her fear by lying about her dreams and putting on a brave face, only to confess in the end, revealing she was scared what the others might think of her if she revealed she was afraid.
The clue was, I admit, a bit of a trick question. The clue states "lies within", which usually means something that is hidden from view, concealed behind a front, sort of speak. So the statement "Fear lies within" was talking about a character who did not appear afraid on the outside, but was terrified on the inside.
Stir up trouble, let it grow
Answer: Littlefoot
Explaination: In LBT11, Littlefoot attempts to eat the tree-sweets, but ends up knocking them down. In an attempt to protect himself, he blames little dinosaurs he saw earlier. This creates panic among the valley denizens, and they start hunting the little dinosaurs relentlessly. Littlefoot makes no attempt to make things right, and he allows the lie and the trouble to grow until it is almost too late.
Stirring up trouble does not always have to be done with violence. It can be done with a simple lie, and allowing that lie to grow out of porportion. This is exactly what Littlefoot had done.
Innovation, key to the future
Answer: Petrie
Explaination: In LBT12, The Great Day of the Flyers was the test young flyers had to endure to be considered old enough to fly with the adults. For generations, it was always the same, a simple coordinated flight where all the flyers soar in unison. Petrie, however, changes all this with his free-style flying. This inspires all the other flyers, including the observing adults, to begin flying the way they want to. Petrie's mother comments that the Great Day of the Flyers would never be the same.
The term "innovation" means doing something new, radical, very different. Petrie's free-style technique had not been attempted before, and it is likely this will stick for generations to come. One little flyer had changed the future with a single innovative idea.
So...whose turn is it to choose the category?