Looks like Mr & Mrs PH got an update in the last couple years. From Wikipedia:
Since 2011, new models of the Mr. Potato Head toys, commonly referred to as Jason, have been produced. The Mrs. Potato Head version of the toy was also brought out in early 2012, commonly known as Rachel, and has a baked bean-like head.
As to fit with other PH's, the spud measurements are on our specs page.