They are male & female (Simon & Stitch) and have been together their whole lives.
He gets a bit amorous at times and starts by running around doing the head bobbing thing, displaying his beard, then he approaches her from behind & grabs her on the spikes at the side/back of her head, but it doesn't last long, (a minute or so) and then he bobs his head up & down a bit more & that's it. It's there natural way when courting, looks a bit rough but I've seen her carry on eating & do a bit of arm waving while all this go's on.