I want to create giant NPCs that can walk and move without problems. I have tried to make a character invisible and weld larger body parts to it. Problem is, the character just goes out of control regardless and some of the body parts would split.
I've remembered seeing a game with large giants and including the Attack on Titans
game on ROBLOX with huge monsters.
How could I create such giants that can chase, move, and etc?
At this scenario I've inspected some 'free models' about this Titan ( as i've played some few games of it before ) and if you will observe the instances inside this model; you can see the default ROBLOXCharacter inside it (some having packages) however, this may lead you to the buff-ish point. In order for you to have biceps and triceps growing in your so-called NPC then you could do the first thing you attempted; welding as ROBLOX doesn't provide any 'buff-NPC' property.
Do make sure that: The [muscle-object] you are welding to the NPC does not block its joints or between two parts (between the neck and the torso for example, or between the leg and torso) as this may disable your NPC from moving properly.