First go to the mu continent and choose character (make sure your game is saved at the point you wish to use the character) , then return to the title screen. Enter the main game without doing anything else. This can get certain characters into places they couldnt normally reach. For example: you can take squidward and krabs to the final boss, or make sandy face herself! This is just one of the many glitches/cool tips I've found.
When the barrels fall from the sky throw them at the jelly jish. When king jelly fish has thunder bolts coming out of it's anus dodge it and throw the barrels. Next he does this jumping thing so he jumps all around the place so dodge. Last this is his ultimate move he has eletric shocks and he moves all on the ground which destroys the barrels so dodge the move