According to IMDB (from which I take information with a large grain of salt), The Mostly Unfabulous Social Life of Ethan Green started filming on August 4, 2004. And continued from then on, presumably. This is David Monahan's first big role in a movie.
Now, David Monahan first appeared as Det. Matt Seely in the S3 episode "Second Chances." He disappeared for a while, until he magically reappeared in "Revealed," then sporadically was on and off the show whenever another detective was needed, or whenever TPTB felt it was getting too boring and they needed some good character interaction. Seely's last episode was "The Elephant in the Room."
Here comes massive amounts of overanalytical character/TPTB stuff!
People we see on the show a lot (a LOT, a lot)
Namely, the main cast/characters.
Jordan, Garret, Bug, and then Nigel, who was a one-off character but was immediately made into a regular because of his immense popularity with the audience. Shortly thereafter Lily was made into a main character to bring in a different perspective.
Max, being Jordan's father, was a main character until the middle of Season 3, since most of the main plot surrounded Jordan and her mother's murder. Also, Ken Howard had other projects he wanted to work on.
Woody was a recurring character until Season 2, when he was promoted to series regular
People we see on the show a lot (kind of a lot)
Really meaning the recurring characters who are around quite a bit (as in, more than one season), but aren't listed in the main credits because they aren't around all the time omgs.
This would include characters such as our Infamous Secretary Emmy (24 episodes over 5 seasons), DA Renee Walcott (14 episodes/3 seasons), Detective Seely (13 episodes/2 seasons). These are those that have been on the show for a decent stretch of time, in a significant number of episodes.
People we see on the show occasionally (whether we want to or not)
This could kind of be squished in with the above section, since it includes three other characters who have been on the show for a good long while, but in fewer episodes. However, in that short time they have developed significant personalities that everyone in the audience recognizes right off the bat.
This includes Garret's Daughter: Abby (10 episodes/5 seasons), Det. Lois Carver (9 episodes/5 seasons), Dr. Howard Stiles (8 episodes/5 seasons), and Garret's Ex: Maggie (7 episodes/2 seasons).
People we saw on the show for awhile (then they mysteriously disappeared)
This is the One-Off Character Section. Also a grounds for reminiscing over the old times when Nigel hit on Trey, when Elaine was human, and when Peter finally made good with Dr. Macy. Basically, all the characters we loved (or loved to hate), but who seemed to only stick around for one season.
This includes Dr. Trey Sanders (Season 1), Dr. Elaine Duchamps (Season 2), Dr. Peter Winslow (Season 2.5-3), Dr. Devan Maguire (most of S3 to beginning of S4), Dr. Sidney somethingorother (Season 4), J.D. Pollack (Season 5), and as a SUPER SPESHAL BONUS: ADA Jeffrey Brandau (Season 5).
Now, Trey was only on a med school rotation, Elaine was killed by that E. Coli thing, Devan supposedly died in the plane crash, and Pollack didn't really disappear, he just kind of...got brutally murdered. Brandau was obviously left behind by Lily. Peter went on to do bigger and better things, and Sidney...is probably still hanging around the morgue. Trey, Peter, and Sidney didn't really get proper send-offs or ends to their plots. The others haven't been mentioned since unless a specific case has required them being mentioned.
This is why they are the One-Off Characters. They don't really even get mentioned in passing anymore, just...forgotten. Which is kind of sad. Not in Brandau's case, but nobody really liked him, anyway.
Back to the main point, People!
Anyway. Bearing all that in mind, the One-Off Characters were usually listed in the main credits, but didn't mesh terribly well with the main characters. Hence them being replaced after a season. Also? It kept things fresh. It may have made the fan base a little irritated at times, but it made sure things didn't get too boring by introducing a new dynamic each season.
Pollack and Brandau were introduced for specific plot arcs, which is why they weren't around for that long.
Sidney...well, I think Sidney was just introduced as a n00b character, since Devan was around all the time (or at least seemed to be), and there needed to be a slightly meeker presence to counter her pushiness.
Yeah, but what about Seely? This whole post was supposed to be about him, right?
I'm getting to that.
According to what TPTB seem to be doing with various characters, I would quite definitely put Seely in the second group of characters. He's been around for more than two episodes, over a span of more than two seasons, and he was introduced as a potential long-term Conflict Character. Sort of like Renee. Whenever there needs to be some good-natured (usually) conflict, they'll bring in Renee or Seely.
Both characters bring another perspective to the group, be it good or bad, and it forces the characters out of their comfort zones, but not to the Point of No Return. Just enough so that they can see another side of an issue.
Also, both Renee and Seely have come to view the morgue as a sort of second home (though Renee is not keen to make this fact known).
Seely obviously doesn't have many friends at the station, but has a sort of grudging friendship with Bug, and gets along fairly well with Jordan. He already knows when to stay out of Garret's hair, and when to ask someone else to do something (even if it costs him his pride). Slowly he learned how to keep snarky comments to himself when it was inappropriate, though he still slips up once in a while, but in general, he has become a much more tolerable person around the morgue. I could even see Nigel and Seely having a friendship of sorts, if he hangs around for a while longer.
Now, Seely was a major part in the love triangle (then...square, once Brandau arrived), but there was never any real friction between himself and Bug, at least on the Lily front. Their personalities just didn't mesh. Once Brandau got thoroughly involved in the plot, Seely started to fade away a little, at least from that plotline. He was still there, just not as involved with the love "square."
Seely was the comic relief in a lot of the episodes he was in; at the very least, he offered a more lighthearted feel to the show so it wouldn't get too dreary.
However, after "Elephant in the Room," the episodes get progressively more morose in feel, the color scheme changed slightly to accomodate that, and quite a few episodes are "downers." This is all to help lead up to the finale, in which Jordan is a suspected murderer and a major recurring character was killed. There was also the Brandau/Lily issue getting resolved, and Bug/Lily being canonically set up as a pairing (hopefully not jumping the shark). That's a lot to get into one episode. Obviously Seely wouldn't be in the finale for that reason, and I think that's part of the reason why the writers kept him out of the final episodes of S5; they didn't want everyone going "but Seely should be here! Where's Seely?" It just made sense.
Also? David Monahan was likely needed for filming on the set of The Mostly Unfabulous Social Life of Ethan Green at that time, before they went into post-production. The timing was perfect, for everyone involved.
Is he gone for good?
I don't think so. As dispensable as he may seem, Seely brings a balance to the cast when Renee isn't around. He also managed to pass the "One Season Death Sentence," when most recurring characters are booted from the group. I think this might be TPTB's way of telling us not to give up hope on Seely yet. He may return.
The beginning of Season 6 will likely have Woody searching D.C. for Jordan, probably with Garret and/or Nigel at his side. Someone will have to step in for Woody's role when a detective is needed at the morgue for another case (presuming there will be another case in that episode). This will probably be Seely. Possibly Renee, but more likely Seely, since Renee's still dealing with a newborn at home.
Filming for Season 6 starts this month, so I'll let you know what new information I'll get.
This is all speculation, yes, but in my mind, it doesn't seem likely that Seely will be gone for good. He has the potential for a long-term recurring character.
Here's to hoping.
Crossposted to detectiveseely and crossingjordan.