I know exactly what to do to make it, I'm just really lazy lately for some reason and all I wanna do is sleep XD
Plus I'm supposed to be doing school work.
Here's a simple version
Press L+R+Up to save a snapshot of your town, press L+R+Down to restore
Code:
94000130 FCBF0000
DC000000 021E3124
F22BF220 00002000
D2000000 00000000
94000130 FC7F0000
DC000000 022BF220
F21E3124 00002000
D2000000 00000000
However, the BEST way to do it would be an ASM routine that works in real time automatically. That way you won't have to worry about pressing buttons or anything before someone leaves your town. You just press once to activate, and again to deactivate.