0x0000

Simplest BHAV of any kind there is. Does absolutely nothing, ignores all it's opcodes, and always returns true. If these appear in maxis BHAVs, it probably means they had a line of code there they didn't need, so instead of deleting it and having to reassign the true and false targets of other stuff, just called the sleep function, and left it.

That's about the only way you'd ever need it, either. Occasionally it's useful to just add a whole bunch of these into a BHAV you're going to really Mess up Modify, and then make your changes one at a time. Then if something goes wrong, you can make the line into a sleep, until you figure out what went wrong, and can go back later and re-point it, without having to add a new one and fill in all the opcodes.