an invalid tangram is what happens when you aren't nice to jack. jack'll say, "hey buddy, watch your head."→[More:] he says that because there's a squirrel in the tree who carries large wooden dogs. when you walk under the tree, the squirrel swings the large wooden dogs at your head(s). you are walking under the tree now. good thing jack was around to warn you. you should be nice to him now.