Relatedish:
A few years back I saw an advert for Primeval on ITV. I could have sworn that I went to college with the girl in it, she seemed so familiar. Everytime I saw the advert I was reminded, and it bugged me no end whilst I tried to remember her name. Eventually I actually watched an episode just to get to the credits and find out who she was... but the name didn't ring any bells. Then I realised she was in S Club 7.
Roll forward to last year and I'm watching one of the Doctor Who specials. One of the actors seemed familiar, but I couldn't place him. Couldn't remember what other shows he'd been in, if he'd been in a band, or whatever. Finally get to the credits and I realise I used to be in the same group of mates with the guy. Felt kinda bad about that... now I've seen the episode again, and he really hasn't changed a bit in the ten years since I last saw him. Don't know why I didn't recognise him.
He was rather good though. I hope he gets more acting work.