If that's a smooth as a close shave, get your little squares of toilet paper ready...
As to the OP (yeah, I went there) I think a shift towards a couple of jokes or whatnot is fine; as Teaos said, if an off-topic discussion appears that seems to have taken on its own life, we'll split it at that point.
BTW, Teaos, you're right. Nazi regime is out. Not just for my sake, either; the brownshirts wouldn't look too kindly on ovine love.
I can't stand nothing dull
I got the high gloss luster
I'll massacre your ass as fast
as Bull offed Custer
I don't mind that threads go off topic, it's to be expected. But when there's a 5 page thread about whether the E-nil had a warp core like the big blue thing in TNG and the last 4 pages are full of discussions about what your favorite drink is, then someone who wants to participate in the discussion about the E-nil is going to find it hard. They have to search through four pages of posts that have nothing to do with the topic to see if anything else has been said about the topic.
I'm not suggesting anyone police or limit the discussions on this site. I'm just saying that if the discussion goes off topic and it looks like it will continue, start a new thread. After all, a thread about the E-nil's warp core isn't the place to discuss your favorite drink.