What are good travel game apps for iPad to entertain a 2-3 year old My wife is to face a 2h flight with our very active daughter and would like to prepare some distractions.

Specifically we are looking for very simple, entertaining games a toddler can handle. We already have "Memory" and she really enjoys it.

It should be as colorful as it can get and interactive where swiping and touching a thing is the most sophisticated gesture she can handle. Doesn't really have to have a goal, just do stuff.
This is an iPhone app, but will work on iPad, It is a game made for toddlers. 

http://www.hogbaysoftware.com/products/bubbles