Continuity mistake: When Catwoman is electrocuting Max, when you see a view of the explosion from above, you can see Max walk off the set through the explosion. It is definitely him, not Catwoman!!! (check the clothing.) (01:50:30)
Hamster
Continuity mistake: When Oswald starts shooting bullets out of his umbrella at his failed mayor speech, the crowd ducks down on the stairs, at the edge of the red stage, laying down their campaign signs. In the next shot some of the crowd and signs have vanished from around the stage, then reappear in the next shot. (01:27:15)
Hamster Continuity mistake: Batman is monitoring the progress of the rocket-laden penguins via radar. At every screen refresh, about one per second, the penguins have moved about half a street, way too fast for the way they waddle. (01:42:25)
Hamster Continuity mistake: During the scene in Schrek's department store, Catwoman has a tail clipped onto her beltline which keeps disappearing. It is visible when she jumps from the trampoline, and smashes open the door to the gas, but is missing in all the other shots. (00:54:00)
Hamster Continuity mistake: When Selina is pouring Max his coffee, the kettle spout changes position. (00:07:20)
Hamster Revealing mistake: On the rooftop, Catwoman digs her claw into Batman's chest, but she clearly just puts her hand flat on his chest and you can clearly see in the first shot no claw is left embedded in his suit. (01:16:25)
Hamster 
Visible crew/equipment: After the policemen shoot Batman, he falls backwards and slides down the circular ledge. When it cuts to a close-up of him dropping on his back to the ground, the hand of the crewmember placing him down to the ground is visible. (01:15:25)
Hamster Continuity mistake: At the point where the Penguin controls Batman's car from his trailer, we see shots from the inside and outside of his trailer. The Penguin rides the mini-Batmobile in his trailer like crazy, therefore the trailer shakes like hell from the outside, however, the shots inside show ONLY the mini-Batmobile shaking, the floor and trailer seem rock-solid.
Continuity mistake: Just after Selina has hit the ground, we see a shot from above, with her lying seemingly dead in the snow. In the next shot the pattern of the snow around her is completely different. (00:27:15)
Hamster Audio problem: When Oswald holds Catwoman's cat down to the bed while she puts his bird in her mouth, hisses and meows are heard from the cat, but it doesn't open it's mouth. (01:03:25)
Hamster Continuity mistake: When Selina puts the pink teddy down the shredder, it begins to spit and churn out stuffing and feathers. However in the next shot of Selina grabbing the frying pan, the shredding of the teddy has mysteriously stopped. (00:30:00)
Hamster Continuity mistake: When the penguin is going through the birth certificates in the library, he finds a certificate and begins to write. The name of the baby on the certificate is 'Peter Lindsey' but the penguin writes down 'Matthew Gruen.' (00:36:15)
Hamster Continuity mistake: The length of the bar which comes out of the side of the batmobile, which subsequently knocks over the clown twirling the batons, changes between shots. (00:13:50)
Hamster Revealing mistake: In the scene where Selina Kyle starts spray painting the wall and closet, you can see there was a previous line sprayed and then poorly covered with another thin coat of paint. (00:30:25)
Continuity mistake: When Oswald is in The Hall of Records, it is snowing heavily. In the next shot of Batman coming around the corner in his batmobile, it isn't snowing. In all following shots it's snowing heavily again. (00:37:55)
Hamster Continuity mistake: When Oswald goes upstairs and finds Catwoman on his bed, he goes over and hangs his hat over the end of an umbrella in the rack. When he picks up an umbrella as he talks with Catwoman, the hat is now in a different position. (01:01:30 - 01:02:00)
Hamster Continuity mistake: When Batman is fighting some goons right before his boomerang is stolen by a poodle, one of the goons attacks him with a metal pipe, which both opponents take hold of in one shot. Batman then delivers a blow to the assailant, the view shifts further away, and we can see that neither Batman or the goon have the pipe, and it is nowhere on the ground nearby. After this, Batman turns to his right to defend against another goon and we see another enemy coming at him from behind, but after the view shifts to another shot and then back to Batman, this enemy is nowhere to be found.
Continuity mistake: When Max Schrek leads the Penguin over to the image consultants, two women standing behind them suddenly vanish. (00:48:40)
Hamster Continuity mistake: When Batman is on the roof, his cape becomes a glider, the glider is separate from his cape as his cape falls off behind him. When he floats down the glider cape once again resembles his regular cape. (01:16:45)
Hamster Continuity mistake: When The Penguin is explaining his scheme about stealing the children fron their cribs and sending them to their watery graves, a black line of spit runs down his chin. When he turns around it's gone. (01:29:15)
Hamster 
Answer: It is poison from Shrek's factory.