I seriously debated it. I loved all my CR in SMK, but ultimately decided not to bring it in. The main reason was that I didn't want to make things awkward for either Zoki (Kaiba), or Lisa (Yugi), since in SMK Atem was dating Kaiba but in Diatu it was always Yugi (Pulse at that time), and Kaiba.

I would be perfectly fine if Mal (and Sylvando too for that fact) wanted to recall the events that transpired in the Magic Kingdom and inform Atem about it. Yes, he would be confused at first, potentially embarrassed by much of it, but ultimately he would find it plausible due to the nature of dimension hopping and the havoc it seems to play on memories. It should be fun!

(Nope you have it correct! That was this Atem!)

Edit: Just imagining his reaction to the mural story alone. "I did what?!" Pricelss.