Telephones are devices in Mother and EarthBound. They can be used by the party leader to contact family members and various businesses, but their primary function is to allow the player to save gameplay progress. The saving function of telephones was replaced by Save Frogs for the Mother series's third installment, Mother 3.
The only person Ninten can call is his dad, and there are two predominant types of telephones in Mother for him to do so. Black phones are free to use, and the very first one is found in Ninten's home, at the beginning of the game. Green phones are pay phones and cost one dollar to use. They can be found in most stores. There is also one other phone-like thing in the game: a man in Magicant who calls himself the Mysterious Mimicker. He functions the same as a black phone. It is noteworthy that in Merrysville there is a man by the Department Store who asks Ninten to answer a questionnaire. At the end of it, he gives Ninten the Phone Card, which allows Ninten to make 50 calls free of charge on any pay phone.
The same telephone color scheme found in Mother holds true in EarthBound: black telephones are free, while green telephones cost a dollar to use. There are also other phone-like things to be found, as well, such as a parrot-shaped phone in Deep Darkness, a man-shaped phone in Poo's palace in Dalaam, and a uniquely-shaped telephone in Magicant. All of these strange phones are also free.
The biggest difference in telephones between the two games is that Ness is able to call far more people than just his Father. He can also call his Mother, which is useful for curing Homesickness, and is also a way to receive the phone number to Escargo Express, which is a much more convenient way to store items with Ness' sister Tracy. The phone is also the only way to order pizza from Mach Pizza, as well as the only way to gain access to the Stoic Club in Summers.
The black, green, and Magicant EarthBound telephones later make a cameo appearance in Mother 3. They are on display in the Empire Porky Building's Hall of Memories. However, they cannot be used, and are only seen by Lucas and co. as their boat drifts by its pedestal.
In the Debug Room in Mother 3 you can change Lucas and Kumatora age by a pay telephone who likes the Earthbound and Mother pay telephones.