Dee Dee (granddaughter)
Fergle O'Reilly (son)
|First Appearance||The Grand-Daddy of All Inventions|
|Voiced By||Christine Cavanaugh|
Just like his grandson Dexter, he also has a laboratory, as shown in The Grand Daddy of All Inventions. However unlike Dexter's massive and high tech lab, his was a small space in his garage. Grandpa is also implied to be smarter than Dexter since, with a relatively simple set up he was able to create a self sustaining power source, which Dexter failed to do with his complex machinery.
- He is Mom's father since Mom refers him as "Dad".
- His design is identical to Dexter's future self, Old Man Dexter, indicating that Dexter inherits both his looks and genius from his grandfather.
- His only official appearance was in the episode The Grand Daddy of All Inventions however, he was mentioned in the episode Old Man Dexter.
- It is unknown what type of relationship he has with his son, sister, and other daughter.