Check (Japanese:チェック Check) is a command in the Mother series.
Outside of battle
The Check command is used to look at objects that can't be spoken to. In Mother, it is accessed by pressing the A button to open the menu and selecting it. In the Mother 1+2 port and EarthBound, the L button acts as a shortcut to both talk and check. In Mother 3, it is no longer an option on the menu; instead, the L and A buttons both check objects and talk to people. When an object can be both checked and spoken to in the Mother 1+2 version of Mother, such as the Dragon, the game will default to the talk command.
The Check command is also a battle command in Mother. Using the check command in battle will reveal the enemy's Offense and Defense stats, their weaknesses and resistances, and, in the prototype and Mother 1+2, a description of them. In EarthBound, this usage was replaced with Spy, which in the Japanese version, is also named Check; however, this skill can only be used by Jeff. In Mother 3, it was replaced with Boney's Sniff.
A battle screen from the unreleased EarthBound 64 indicates that Check was going to regain its in-battle usage from Mother, rather than being replaced by Boney's signature ability as in the final version. As Flint was shown using it, it is likely that the Check command was planned to be available to all playable characters, as in Mother.