Time Machine drive question.

Right guys. I have just bought a MBP from my housemate and his new MBP arrives in several days. I have a Time Machine of my old iMac with all my documents and software etc that I want to restore to this computer. However my friend doesn't have any spare external space to put his files on until his arrives. I have around 80gb left in my Time Machine HDD. Is it OK to try putting his files into a folder on this drive. I just thought by adding files that are not added through Time Machine may cause TM to not be recognized when I try the restore?

Am I safe to think that even if this was the case it just wouldn't restore and I could then return to OS X and remove those added files and then carry out the restore when he can back them up. Just alot of the stuff I need for university are backed up via TM and want access to them sooner rather than later.

Thanks guys.