unusual question

In theory sure.
No idea how accessible those iMacs are. I don't own one.
Since it is 2.5" you also might need some stuff to fix it in place unless iMac use 2.5" too. Could be don't know. Can be anything that doesn't impair cooling too much and if you don't move the imac too much.

In theory the kernel should just load straight up even if you put it onto another machine.
Worst case you need to backup and reinstall clean.

 

It's not unusual to have a drive swapped by anyone
It's not unusual to have partitions with anyone
but when I see you needlessly wasting time with anyone
It's not unusual to see me cry,
oh I wanna' die
It's not unusual do a TM back up any time
but when I see you swap drives it's such a crime
if you should ever want to told how to do this more easily by anyone,
It's not unusual it happens every day no matter what you say
you find it happens all the time
Multiple HDD swaps will never do what you want it to
why can't this crazy tech be mine


Really though, I think it would be easier for what you're doing to get and external drive, grab the stuff you want from your parents computer and either put it on your existing drive or on the new MBP drive.

 

I'm impressed! Of course, now I can't get that song out of my head!

 

iMac in target disk mode, time machine backup from old MBP.