Be careful, because they CAN screw this up.
When we checked in at SSR in December, I asked to have my in-law's MYW passes added to their room keys (one less thing for them to deal with). They did that, and offered the originals back as "souvenirs" (which I'm glad I took), she just wrote and X and a Mickey head on the back of them.
Well, get to Epcot a little while later...DW and kids go through fine, MiL goes through fine - but FiL can't get in - says he has no park entitlement at all!
We go to the Guest Relations window, and she confirms that the room key has no other entitlements on it at all! This was very strange, because the SSR concierge took the original room keys and issued new ones that supposedly had the entitlements on them! The GR CM gave him a one day pass, and we'd have to get it fixed at SSR.
When I got back there, I went back and explained what happened. Fortunately I had the originals still, and they were able to look it up - and somehow the original CM issued the entitlement to someone else! Someone out there has a KTTW card with an 8-day park hopper that hasn't been used yet
They didn't have any way to remove the entitlement and put it on the correct card it seems - but they did issue a completely new park hopper - but they had to issue it on a separate card, which looked pretty much like a KTTW card - so FiL spent the rest of the time trying to figure out which card was needed where.