Grandpa is a large elderly purple Bubble Dragon with a long white bear and bushy eyebrows. Like most Bubble Dragons, he has a single visible tooth in the upper middle part of his mouth. Grandpa has yellow spines and pink arms and legs, and is always seen carrying a wooden staff.
Grandpa is shown to be kind and wise. He cares for his grandchildren greatly, going so far as to organize a fake treasure hunt in order to send the three off on a journey as a gift to them.
After reaching the location marked on the map, the trio discovers a golden treasure chest, from which Grandpa emerges. Grandpa reveals that the map was fake, and that he had orchestrated the journey as a gift to the three. He then gives them the Heart of Courage, and tells them to never forget that courage will always be with them.
- Grandpa and Bubu are the only two Bubble Dragons in the entire series with any direct relation to Bub and Bob who are not shown in human form at any point.
- It is unknown which side of Bub and Bob's family Grandpa hails from, as neither of the twins' parents appeared in Bubble Bobble Double Shot, nor was Bub and Bob having a grandfather ever specified in previous games.