In the Phineas and Ferb S1 episode “Tree to Get Ready”, Doctor Doofenschmirtz lists a lot of people he wants to take revenge on, besides his brother Roger and Perry the platypus.
I bear lots of animosity to bellhops,
They never bring my luggage up on time
And taxi drivers really tax my patience,
If they vanished, would it really be a crime?
I don't like meter maids or underwater welders,
Health fanatic cooks or camera crews!
Not fond of monks or yoga teachers,
Or sports fans in the bleachers!
Does Doctor Doofenschmirtz have a scheme targeting any of the people listed here any time in the show?