If you “cross” A with B, you mix or combine them. I am an English South African, I could say my culture is English crossed with South African culture.

In this context the verb "Cross" is a short form of "cross-breed". It means to mix genetically. Imagine an elephant that can jump like a kangaroo. That's where "big holes' come from.

Cross with — as in mix with — almost like a cross breed — so crossing an elephant with a kangaroo, it wants you to imagine that there’s an elephant hopping around like a kangaroo — get the joke — ha ha !

'To be cross with' is another phrase for 'to be angry with.' For example: I am cross with Andy. He was mean.