I was watching Phineas and Ferb's Quantum Boogaloo and in the time frame 20:11, Linda says, "Candace, my Phineas and Ferb are 30 years old now."
And the Time Machine took them exactly 20 years in the future, so Phineas and Ferb are 10! Well, they were 10 at that time, and Phineas is 11 now (Because of his birthday).
1 mystery down! Many more to go.