During Joey's "Big Break" he gets a job playing Dr. Drake Remore' on Days of Our Lives. Now anybody who ever watches the show knows that his character doesn't exist (which is no big deal). However, even more importantly, Days is filmed in Burbank, California, and Joey (obviously) lives in New York.
It's just a show. Shows aren't going to be that realistic. If they were, they would be copying the show Days Of Our Live completely, and they can't make Joey play a character that DOES exist, because the real one wouldn't be him. I'm sure the show Days Of Our Lives wouldn't allow that kinda thing.
I think it is a very valid point. I'm from Australia and didn't know where Days was filmed, but now that I know, it kind of makes it pretty silly to think of Joey traveling there!
I think the whole point of having Joey on Days is that it's a well known soap opera that is on NBC. If you notice most of the shows featured on Friends are NBC shows (Tonight Show with Jay Leno in TOW Mrs. Bing) I think that goes for all sitcoms on NBC (such as Will and Grace when in the episode where Jack and Karen meet the actress who plays Lillith, they frequently refer to Friends and Fraiser, and another time when Will and Jack kiss during the Today Show in front of Al Rocker[sp?])