I will agree that that comedy comes out of nowhere and honestly doesn't fit in with the rest of the movie, but it felt to me like THIS was the movie they were trying to make now and the rest fell short, rather than the opposite (of course, this was the first Lethal Weapon I'd ever seen).  The scenes work far better alone than they do with the rest of the movie, though.  Or maybe because the last time I was watching them, I watched them all in a block and I was getting sick of the whole down and bleakness of it (it felt tacked on in this movie- honestly, the stuff like "we got a new sign: no vacancy" felt more forced and uninspired) and wanted something more lighthearted.  Or something like the later Trek flicks where you know that the cast is too old to do the old stuff and so the nature of it has to change accordingly.

At least it served as a general audience introduction for Jet Li.  He would have been awesome in an earlier flick like this.  But I KNOW Glover and Gibson couldn't realistically take him down in a fight, so that whole thing never worked for me.