Hildegard Johnson also known as Hilda is the grandmother of Jeremy Johnson and Suzy Johnson and mother of Jack & Joe Johnson. The Johnson family greatly respects her, as the The Johnson Family Picnic is held on her birthday every year.
Hildegard was part of the rollerskating derby early in her adult life. Her team, the Saskatoon Slashers, won against the Tri-State Bombers. Ever since then, Betty Jo and Hildegard have been enemies. After a re-match in Phineas and Ferb's roller rink, the race ends in a tie. They still disagree about who won the race ("Crack That Whip").
During the Johnson's Family Picnic, Hildegard had her 85th birthday. She says that she doesn't like Candace, but she changes her mind when Candace finds Annabelle, who is the long lost member of the family. She recognizes Annabelle's status as a member of the family due to Annabelle's birthmark which is the letter "J" ("Run, Candace, Run").
It is shown that Hildegard hates losing. She initially disliked Candace. She then changed her mind about her when she returned Annabelle Johnson to the family.
Suzy seems to admire her grandmother, as Suzy has shown compassion, the latter even hugging her grandmother. During Hildegard's rematch against the Flynn-Fletcher family, she automatically asked Suzy, indicating that she is somewhat aware of her granddaughter's darker persona ("Crack That Whip").
Hildegard seems to command great respect amongst her grandson, as he sportingly "battled" against the Flynn-Fletchers ("Crack That Whip").
When Annabelle was little she "wandered off", but when Candace brought her to the Johnson's family picnic, Hildegard was so overjoyed that she changed her opinion of Candace ("Run, Candace, Run").
Hildegard and Betty-Joe are rivals from their days in the Tri-State Roller Rink. Hildegard pulled a dirty trick to win, and Betty-Joe accused her of cheating. The two mellowed and found common ground (or at least attempted) for the sake of their grandchildren ("Crack That Whip").
Hildegard said that she didn't like Candace, likely for being the granddaughter of her old rival. She took a liking to Candace when she brought back Annabelle ("Run, Candace, Run").