Dude, We're Gettin' the Band Back Together! (Part 1 & 2) - S1-E22
Continuity mistake: During the song at the end, there is a zoomed out shot of the entire crowd. You can see Phineas and Candace both screaming with their hands in the air, their eyes closed, and Phineas is not holding a camera. When the camera instantly cuts to a close up of them, both of them have their mouths closed, their hands down, their eyes open, and Phineas is holding a camera.
Eeyore's Tale of the Missing Tail / Pooh, Light Up My Life - S1-E4
Continuity mistake: In "Eeyore's Tale Of The Missing Tail", Lumpy ties the rope and rock to Eeyore, but when the Super Sleuths come it is gone.
Burple Nurples/Shnitzel Makes a Deposit - S1-E2
Continuity mistake: In "Shnitzel Makes a Deposit", Truffles tears off a check from a checkbook and gives it to Shnitzel. A few shots later, the page where she tore off the check is back to normal.
Continuity mistake: Chris says he is handing Heather the final marshmallow of the night. When the shot changes for Heather to yell at the rest of the team, Chris is holding a full plate of marshmallows.
Rocket to the Moon/The Birds - S1-E3
Continuity mistake: "The Birds" - Sheep has the egg in a baby buggy next to the basketball court. She and the buggy are at the side lines. One of the others accidentally hits the ball towards the buggy and Sheep blocks it with her face, scoring a goal. Suddenly she and the baby buggy are in the center of the basketball court.