Yeah, the E. lactea crest is grafted onto E. nerifolia, or Indian Tree Spurge. The spurge has decided to sprout a branch. The branch can be cut off or removed and rooted when it got a bit larger. I guess it's not that uncommon to see the root stock put out a branch, but it does look weird!

I think it looks cool;). They never have these grafted Euphorbia lactea crests at my Lowes. I’ve never seen them once. Which is strange because it seems like every Lowes across the US has them.