Well here is what happened:

I originally booked a flight to Las Vegas during one of AC's daily web saver sales and I got my flight for $288.43 RT taxes and all in. WOW never even paid that much when Jets Go was even around and going on this flight with 3 other buddies as well. So my flight path as follows:

Going:
YYZ 8:40 DEN 10:13 (on AC)
DEN 13:54 LAS 14:53 (on United)

Return:
LAS 18:46 SFO 20:00 (on United)
SFO 22:20 YYZ 6:13+1 day (on AC)

This was perfect as I was able to spend a few extra hours in the warm Vegas Sun. But then my only friend that doesn't have AP calls me up and says that he just got an email stating that AC changed his flight back to YYZ. So I checked mine and as did my other friends and we had been changed and we all had booked separately. Our new return looked like this now:

LAS 15:15 YYC 19:10 (on AC)
YYC 00:20 YYZ 6:07 (on AC)

Well it was sort of good as well as we would have had to pay for 2 half day room rates as our rooms were comped by MGM.

I guess I have more than one question here from this situation:

1.) Can AC do this?
2.) What is something fun to do in YYC during a 5 hour layover
3.) Is it possible to leave the airport after clearing customs in Calgary?
4.) I have never had a Canadian stop before getting to Toronto from the US or any international destination and wonder if I would clear customs in Calgary or Toronto?