Does the dance floor in the nightclubs ever really get busy the one i went in yesterday only had my sims dancing

I've never seen them busy... I've seen 3 or 4 max on the dancefloor. It'd be really good to see it busy!

If you have your sims call over other sims they often start dancing too. Or you can start the smustle and watch the entire lot start dancing.

But sims left to their own devices seem to prefer kicky bag and pillow fights over dancing.

is there an actual dancefloor object? i can't find it.

It's a 1x1 rug that you lay out however you want it. It is a shiny white thing that looks like something for a bathroom in the catalogue. (In fact, that is where my first one ended up) As soon as you place it it turns red. After you place it you can go in in "live" mode and configure its changes to one of 8 settings, with or without block fading and/or random timing. All the blocks are set with the first one, so you don't need to do a 5x8 floor piece by piece. But if you have OFB, don't put it on an interior foundation, because nobody seems to climb up onto those. (On the other hand, that is a lovely place to hide the musical instruments, bubble blowers and rc cars you don't want them playing with right now.)

Can the nightclub actually work without this object? Because I can't seem to build a successful nightclub. I'll put the in the dj booth but the lot always crashes when I try to load it in live mode. I'm wondering is it because I don't use this dance floor object.

You don't need these tiles for a nightclub to function as a nightclub. All you need is any object that Sims will dance to.

you can make the other sims selectable, and then let them dance, then change them to unselectable again...

you can do that by "insim" or the cheat (boolprop testingcheatsenabled true)