Bob is obviously quite relaxed with Marley. They sleep together often. But when they play with each other it looks like Marley is going to kill Bob. Marley's long mouth is open wide like an Alligator and she seems to be trying to gnaw through Bob's throat. Bob's arms are either softly embracing Marley or Bob looks dead: limp on his back, legs splayed, tail relaxed. Then Marley switches her attention to taking Bob's mouth and nose into her gnawing jaws. She makes a moaning kind of vocalization. Bob occasionally squawks. I make Marley back off and Bob pounces on the obedient Doxie, doing all the same things to Marley that were done to him.
Bob will walk away like a matador, then turn with his ears back and flat, whirl and make a run at Marley. Sometimes he attacks and sometimes he just pretends to attack. It's a very engaging play. I wish I could film them.