First you need to have the Banjo Kazooie arcade game. Then, in Banjo Kazooie find the six colored eggs and the ice key. Now find the seven secret spots in Banjo Kazooie NAB and there will be a mumbo crate on each one once you obtain that secret item in Banjo Kazooie.

Vehicle	How to unlock
Beacon	Find the green egg in Banjo Kazooie then it will be in the cave under LOG's game factory.
Disco Ball	Find the red egg in Banjo Kazooie then it is beneath the Terrarium of Terror. Walk down the tunnel next to the wrench-it switch.
Flag	Find the ice key in Banjo Kazooie then it will be on top of boggy's gym.
Fluffy dice	Find the pink egg in Banjo Kazooie then it is in the boathouse under Banjoland doors.
Goldfish	Find the blue egg in Banjo Kazooie then on castle turret that overlooks the docks.
Googly Eyes	Find the yellow egg in Banjo Kazooie then on the beach below the lighthouse. You need the horn to obtain this item.
Mole on a pole	Find the cyan egg in Banjo Kazooie then it is on rooftop south of the jiggy bank acces via drain pipe near the canal.