Phineas and Ferb Wiki has a collection of images related to Title cards.
A title card is the shot at the beginning of an episode to help viewers identify the episode. Many scenes show outside of the Flynn-Fletcher house, but sometimes extends to the scene or at a completely different location.
Starting from "Summer Block Buster", the title cards have increased in size and are always shown at the bottom of the screen to reflect the transfer to HD, and the font color changed from white to pale yellow.
