2 1/2 CSIs

In the past, I've blogged about how much I love crossover episodes of two different TV series. Detectives from "Homicide: Life On The Street" would appear on "Law & Order" and so forth.

But tonight begins one of the weirdest TV crossovers ever. Tonight's episode of the hit sitcom "2 1/2 Men" (CBS, 9 p.m.) was written by a writing team from "CSI" and includes a guest starring appearance by "CSI" star George Eads as a crime scene investigator.

On Thursday, the "Men" writers return the favor by scripting this week's "CSI," about the murder of a difficult sitcom star (Katey Sagal). That episode is supposed to be full of in-jokes, since it was written by "Men" creator Chuck Lorre, who had a notoriously stormy relationship with Cybill Shepherd when he created her sitcom "Cybill" in the mid-90s.

It's certainly not a crossover that would have ever occurred to me. It's not like I watch either series, but I can't say the thought has ever popped up during a drama that said "Boy, this show would be much better if it was written by sitcom guys."

On the other hand, the switch could be a positive one for a couple of reasons. For one, shows that have been on the air for a while, even if they are hits, could use a shake-up from time to time, and bringing in different writers with a fresh perspective is one way to do that.

Another positive is that the writers themselves get to stretch their creative muscles for a bit by writing something completely different, including a different format.

My guess is that the "CSI" episode will work a little better, because comedy is one of the most difficult genres to write, and Lorre is bringing a lot of his own background into the "CSI" episode.

I'm wondering if both episodes do well, will CBS continue to switch around more writing staffs, and will other networks jump on the bandwagon? Perhaps the writers of "Numb3rs" could do an episode of "How I Met Your Mother," in which Barney uses complex mathematical algorithms to optimize picking up women, while the "Numb3rs" team from 30 years in the future recalls a case from 2008.

The possibilities are endless.

"MEN IN TREES" AXED: ABC won't be renewing "Men In Trees" for next season, TVGuide.com is reporting. The Anne Heche series jumped around the schedule a lot, making it difficult pick up an audience.

MONDAY'S BEST BETS: By the way, there are plenty of drama writers who can do comedy just fine, so I'm not dissing the "CSI" writers with tonight's "2 1/2 Men," which anchors new episodes of "Big Bang Theory" and "HIMYM," and is followed by "Rules of Engagement." Although I have to point out, "CSI" isn't as unintentionally funny as "CSI: Miami." (CBS, 10 p.m.)

For example, some of the best comedy writing of the season was done last week on "House" (Fox, 9 p.m.), as House and Cutthroat Bitch battled for custody of Wilson, who just hung around in the background helpless against the schemes of his best friend and his girlfriend. This week, House (Hugh Laurie) kidnaps his favorite soap star when he diagnoses him while watching an episode. It follows a new "Bones."

ABC sandwiches "Samantha Who?" (ABC, 9:30 p.m.) with "Dancing With The Stars" and "The Bachelor."

"Gossip Girl" (CW, 8 p.m.) has a character outed out of the closet. It's followed by "One Tree Hill" at 9 p.m.