Other mistake: When Drake and Josh are in jail, Drake is making a call on the pay phone. But if you look close you can see he just dialed "2" over and over.
Other mistake: Drake asks if he can have a Doctor Fizz and his father replies that they are all out. In the next scene with Megan and Josh, in the background there is a full bottle of Doctor Fizz.
The Peruvian Puff Pepper - S3-E2
Other mistake: Drake and Josh find the monitor in Megan's room. After they reveal the normal wall and the family leaves, Megan hits the button behind the picture to show the monitors. However, when Drake and Josh find out that Megan entered the salsa competition, they storm into her room, but the button is still revealed in the background.
Helicopter - S4-E19
Other mistake: When the dad has some of the "soup", he eats it with a slotted spoon.
Chosen answer: Well, she is the most liked sibling, so she can probably get more out of her parents, or get money from both of them without the other knowing, or as we saw in the Gary Grills episode she can get money from people easily by telling them all sorts of stuff.