The Blubbug is a orange member of the Bloather Family featured in Hey! Pikmin. They have a thick layer of fat around their body, which can cause Captain Olimar or his Pikmin to be bumped into hazards.
The Blubbug is a docile creature that cannot cause any direct damage to the Pikmin and cannot be killed by Pikmin. It can however be pushed down a pit if Olimar repeatedly throw Pikmin at it. Olimar and his Pikmin can also jump on its head if the Blubbug is in a suitable place.
Hey! Pikmin Log
"Not only does its thick, rubbery layer of fat insulate it from the ice and snow, it wards off any attack. The only way to get at it is to attack its inner core. It has that in common with certain people I know. It's just impossible to get through to them past their thick, insulating layer of self-regard."