Mrs. Johnson

 who allegedly also goes by "Hawkeye" Johnson, is the mother of Jeremy Johnson and Suzy Johnson and wife of Jack Johnson. She is the sister-in-law of Joe Johnson and probably the daughter-in-law of Hildegard. She is also related to Annabelle. She is in the Free-Form Jazz Band alongside Linda Flynn-Fletcher and Vivian Garcia-Shapiro. She has appeared several times (mostly in background shots).

Suzy Johnson
Suzy and her mother have yet to be seen interacting but it is safe to assume that she is unnaware of Suzy's darker personality.

Jeremy Johnson
It appears that Jeremy and his mother are quite close and Jeremy often helps her with anything animal. ("Misperceived Monotreme", "Bad Hair Day")

Candace Flynn
She gets a good impression of Candace after she "saved" a tangerine orangutan which happened to be Heinz Doofenshmirtz covered with Candace's hair. ("Bad Hair Day")

Background Information

 * Jane Lynch from Glee recorded dialogue for Jeremy's mother on January 13th, 2010, to be used in "Run, Candace, Run" and spoke for the first time in Canderemy.
 * She has an Associates degree in Zoology ("Bad Hair Day").
 * She calls herself "Hawkeye Johnson". Most likely, because she has a good aim ("Bad Hair Day")

Appearances

 * "Flop Starz" (First appearance)
 * "The Fast and the Phineas" (Non-speaking cameo)
 * "Raging Bully" (Non-speaking cameo)
 * "Run Away Runway" (Non-speaking cameo)
 * "Mom's Birthday" (Non-speaking cameo)
 * "Jerk De Soleil" (Non-speaking cameo)
 * "Dude, We're Getting the Band Back Together" (Non-speaking cameo)
 * "Comet Kermillian" (Mentioned only)
 * "Phineas and Ferb Musical Cliptastic Countdown" (Non-speaking cameo)
 * "Just Passing Through" (Non-speaking cameo)*"Canderemy"
 * "Run, Candace, Run"
 * "Bad Hair Day"
 * "Gi-Ants" (Cameo)*"Let's Bounce"