I'm not sure how successful this post will be I'm giving it a shot anyways!
I played this point-and-click, 2D adventure game back in 2000 so it was obviously released before then. It was all colourful and cartoon drawn, more like Monkey Island than Kings Quest. You played a male character who "might" have been a detective (this is fuzzy) and I recall in the beginning of the game being backstage at some performance (opera or something).. I believe you were trying to speak to a woman but you were attacked by some "thugs". I think you were then tied up in some room above the theatre and had to escape. After this what I remember is being in a museum (It was brown inside and had a checkered floor). There was a skeleton of a dinosaur up and I remember going into someone's office on the top floor. I can't remember if someone was in there or not.
That's all I've been able to recall and I've been thinking about this for quite some time! If anyone has any idea of what game this might be, please let me know. I've already scoured old game archives like The Underdogs and the releases on this site and nothing seems to ring any bells.

The bit about the museum and the dinosaur is ringing some bells, but I honestly can't remember the game I'm thinking of.
The only other cartoon-style adventure I can think of which might fit is Flight of the Amazon Queen. It does start off in a backstage type area, there are thugs, and there are dinosaurs, but it doesn't quite match.

It made me think of Flight Of The Amazon Queen too. Brilliant game, BTW. A wonderful parody of all those old 50s sci-fi/horror b-movies.

AH HA! Yes That's exactly the game it was!
Thanks a lot!

Thanks RandomSkratch!
By the way, welcome to gog and the forums.
Runaway was a very different game (too bad it had Starforce as I recall). I never finished it but I made it quite a ways through the game.
It would be rather nice to see it come to gog DRM Free; also the followup title as well.

And FotAQ runs through ScummVM too, so compatibility is not a problem. Just download it from the ScummVM site, and you're good to go.
Otherwise, I expect it'll turn up here on GOG at some point.

I don't know about the rest of your points, but this exact moment happens in Indiana Jones & The Fate of Atlantis.

Hmmm maybe I am combining a bunch of games together! I've played so many of these (and have loved every one) so I guess they're all starting to blend into one big epic adventure game in my mind.