The Calgary Comic Expo is the 6th largest of it's kind and it's history gives its own right. John Barrowman, Eve Myles and Gareth David Lloyd are being reunited at the Calgary Comic Expo.
The seventh Doctor, Sylvester McCoy, and Mark Seppard will also be at the expo. You can see their schedule's below.

Friday, April 26	Saturday, April 27	Sunday, April 28
12:30 PMAutographs 5:00 PMAutographs 8:30 PMSpecial Event (Fairmont Hotel)	10:00 AMAutographs 12:00 PMTorchwood Panel 2:00 PMAutographs 3:00 PMPhoto Ops 4:30 PMAutographs 6:00 PMPhoto Ops	10:00 AMAutographs 12:00 PMSpotlight Panel 1:00 PMPhoto Ops 4:00 PMAutographs

Friday, April 26	Saturday, April 27	Sunday, April 28
12:30 PMAutographs 3:00 PMAutographs 4:30 PMPhoto Ops 8:30 PMSpecial Event (Fairmont Hotel)	11:00 AMAutographs 12:00 PMTorchwood Panel 1:00 PMAutographs 3:00 PMAutographs 6:00 PMPhoto Ops	11:00 AMAutographs 1:00 PMPhoto Ops 2:00 PMAutographs

Sylvester McCoy does not have a schedule available right now and Mark Sheppard is only there for Saturday and Sunday.

There are many other guests appearing at the convention that may interest you if you're a fan of other shows. You can see these here.

Most of the tickets are now sold out, but some are still available. You can check out more information here.