Kitten-class attack ships

Kitten-class attack ships are a type of Nibblonian spaceship. They can be defeated by chairs. Supposedly they are the pride of the Nibblonian fleet, as Nibbler states when they were defeated "Even our Kitten Class attack ships were useless against their mighty chairs" indicating their importance and reputation.

Additional info
Their name could be referencing the common stereotype that Nibblonians are pet like creatures and are "too cute". As the ships were pathetic in flight and resembled a harmless toy.