Articles should be written as if you are there watching the events take place as they happen, and should indicate some familiarity with the characters. This is called "writing in-universe". For the most part, descriptions are written in present tense, though past tense may also be used when describing a historical event shown in an episode. Example: Phineas and Ferb are sitting under a tree, wondering what to do today. Contrast this with: In the episode "Rollercoaster", Phineas Flynn and Ferb Fletcher were sitting under a tree.