True, did the Ellimist create the Time-Matrix? Was the creater of the TM ever solidified? If not, it could've been the being that created the TM that laughed.
If it's the Ellimist that was speaking to Elfangor at the end of TAC, then he did make the Time Matrix, because he refers to the TM as "his machine" (or rather "our machine" because the Ellimist likes speaking in the plural for some reason. The Andalites apparently believe in "Ellimists" as a group, rather than one "Ellimist")
You could argue that Ellimist was really speaking for all hyper-dimensional beings when he introduced himself as one of "the 'we' whose machine you have used to alter the direction of time and space," though, but I never really thought Ellimist would deign to speak for Crayak and whatever other powers inhabit his dimension. Then again, he says that that same "we" are playing a game with another power, which is presumed to be Crayak.
I'm rather sure Crayak wasn't the one laughing. Remember, this was the part where Ellimist was "stacking the deck" against Crayak and the Yeerks. Drode was pissed about that in MM4, so I don't think Crayak would laugh about it.
As for The One, because he was introduced in the last chapter of the series, there's really no indication as to who or what he is. I think most people assume he is either Crayak, some subordinate of Crayak's (perhaps the being that was destined to "absorb" the Yeerks as Ellimist said in the beginning of #26), or the being that forced Crayak out of his domain.
We don't get any indication of the being(s) in #41 either, except that they are not Ellimist and presumably not Crayak either. My own theory is that the beings who created the "fake future" are the Orff, who put themselves into the simulation in order to observe and interact with Jake. That's just my explanation, though, in lieu of an official one.