Many years ago I saw former Warwickshire and England cricketer Dermot Reeve break up a fight in the Dome nightclub in Birmingham
And when I have attended Comic Con with my son, we have interacted with:
Colin Baker (Doctor Who) - lovely bloke, very chatty and happy to pose for selfie photos (which seems to be a rare thing these days)
Mark Williams (Fast Show, Mr Weasley in Harry Potter, Mark Williams on the Rails, "We wanna be together" advert etc...) - again, lovely bloke and happy to pose for selfie photos
Sam J Jones (Flash Gordon, Ted 2) - was nice but in a bit of a rush so we didn't get chance to thank him for saving us all
Chris Barrie (Red Dwarf) - was not as tall as I thought, don't believe he really wanted to be there
I read a few years ago that Chris Barrie was going to stop comic-cons for a while as he got bored by them and got annoyed with constantly being asked to do the salute and only being known for being Rimmer and not for his other notable work. Craig Charles has supposedly got better in his advancing years after his personal issues, he did a DJ gig a few years ago near me and people that went there said that he was charming and really down to earth, although sometimes I have to turn off the Gadget show because he can be a bit O.T.T at times, the other two I am unaware of but Llewellyn seems a nice guy, Norman Lovett (Holly) was at a comic-con last year, but never got to meet him.