The act of 'head-pressing' added in Megamind’s culture could be a significant, rooted act and one that could definitely be cannon—
Imagine: a sea of blue aliens bumping foreheads in a collective surge of excitement or shared emotion— like a family gathering— much like a group of affectionate cats just head butting one another.
It’s sweet, until you consider the logistics that Roxanne probably sports a few faint bruise from when Megamind’s enthusiasm took over his coordination. While their massive craniums look delicate, they must be built for more heavy impact, capable of taking a little more force than a standard human skull.
(Megamind and his parents head-butting is something I’m very fond of imagining)