This is a good idea, if you remember to always tell the same lie. Being required to remember which website I told which lie to can only lead to trouble.
Some password managers will generate a pronounceable string for you too, saves coming up with anything witty...
Since security questions are typically used for things like password recovery, you probably shouldn't manage them with the same tool you use to manage passwords. After all, if you need them, it is likely to indicate a critical failure of your access to (or your data held in) that tool.