Quest for the Spark
Fredrick is a dead squirrel corpse within the series, he was first seen by Stinky and Smelly but Agak took him. The rats take Fredrick from Agak, but not before waking the king up. After Stinky and Smelly are aboard the Queen of the Sky, a piece of the Spark is discovered inside Fredrick and is removed.
Quest for the Spark 2
In Quest for the Spark 2, Fredrick had screwed up another plan of the rats and ultimatly caused them to save Tom and Roderick.
Quest for the Spark 3
Fredrick is a dead sqirrel.