Ash and Checkers are Obscurus Lupa's two cats. As she puts it herself: "She’s [Ash] the fat, angry one that goes “EEEEEEEH!” ... He’s [Checkers] the skinny, stupid one that goes “HUH HUH!”"
Originally featured in one of Lupa's videos as a gag, they have since become recurring characters (particularly Ash) to deliver jokes in Lupa's distinctive voices.
The animation on both is a very simplistic style done with what appears to be Microsoft Paint and two frames of animation.
The real Checkers passed away August 5, 2013.