Is it possible?

if you want to walk in it, not feasibly.

However, we could pin a craft to it and make it pick up people and transport them on flat land?

It is possible I think. Lua can probably be used to stick turrets on the crab and then were good to go.

Although what this thread should really be about is massive bosses.

I was thinking just today about some bosses for official content main/side missions such as a armored ronin gunship, a large robot with laser or some very badass organic wildlife monster with gigantic claws (think: starfox64 titania boss)

I have ideaz:
Try making a mini space ship out of thundertoes sprite in the sprite dump. There was talk about making it a boss monster, but loooong ago.

I'm worried that it will accidentally pick itself up and crash the game, or worse, die.

I've got a clone with turrets attached to him. Making a giant crab with turrets attached to him isn't hard at all.

what do you mean mad turrets

To stop it picking itself up, try making the doors actually point away from the actor.

Look at luaguns for help.

Test it out though, with a drop crate, see if it even works. If its an ACrab, how would you tell the ARocket to open its doors? use lua to add the button?

Good idea. Or you could control the craft and open its doors manually.

can you control a craft thats attached to a crab? I figured it would be part of the crab and they'd share health or some crap.

No, it's two separate actors, just pinned to each other.

What about going small before talking about huge ass crabs?

p3lb0x wins so far.
you cant walk on actors currently though due to the way mo-mo collisions are handled.. but you could have a bigass robot crab with pwnage weapon systems and overshielding.