Did it look like this?

Osage Orange
http://www.mitzenmacher.net/blog/wp-content/uploads/2006/10/Osage%20Orange_004.jpg

Here is a link that might be useful:

If they are really monsters it may be a Ponderosa Lemon. My husband bought a couple and when he brought them home they almost frightened me. They are indeed lemony in taste. the peel can be cut in thin slices and cooked in heavy sugar syrup for a candied lemon peel confection.