iMovie: Some special characters (Unicode) do not display in titles

Symptom
Using some Unicode-only characters in iMovie titles may result in the character being displayed as a blank, question mark, or rectangle when the title is rendered. The character may also cause the rest of the title past the character not to render.

You normally enter the affected characters with a combination of keys (such as Option-E + apostrophe) or with the Character Palette.

Solution
Use Key Caps or the Keyboard Viewer to see if there is an alternative way to input the special character you need. If you do not see the character you are looking for, try using a different font that can display the character you want without pressing a combination of keys.