All communication between Mars and Earth goes through satellites. Because of the distance, there is a substantial delay. As communication signals travel at the speed of light, this means that it can take between 3 and 22 minutes for the information to reach the other end, so a phone call would not be practical.
Evaporated milk, also known as dehydrated milk, is a shelf-stable canned milk product with about 60% of the water removed from fresh milk. It differs from sweetened condensed milk, which contains added sugar. Sweetened condensed milk requires less processing since the added sugar inhibits bacterial growth.
Stitch is a blue, koala-like, alien genetic creation standing around 3 feet tall. He is referred to as a dog throughout much of the franchise, and was thought in the beginning by Lilo to be a collie hit by a car, and Nani thought it was a koala of a sort before they found out he was a genetic experiment.