Tweak is the engineer for the Octopod. It is her job to make sure that everything is 'shipshape' below deck in the engine room and to maintain all the Octonaut vehicles. She has even invented a number of new machines for the Octonauts, most notably the Gup submersibles.
She likes to build and fix things, but she does not like how Kwazii or Shellington crash the Gups (mostly the Gups B and D) and is forced to fix them again and again as a result.