I'm a complete amateur with animation, but had a couple of thoughts about this anyway :) Is the viewpoint from above the floor all the time? If so............could you animate it by making the string as a very long narrow cylinder, keyframe the movement of the leading object, once it's disappeared through the hole you can start chopping off segments from the end of the 'string' and wobbling it a bit to make it look like it's moving. Does any of that make sense? The object that re-appears through the floor needn't be the same object that goes down the hole in the first place, could be a duplicate with a short string trailing, maybe easier to manipulate. Uhmmmmmmmm - can I explain what I mean a bit more clearly. Object #1 with long tail goes down the hole, once it's out of sight it can stop moving, and the string gets the end bits chopped off gradually the whole way through the animation, to simulate movement. At a certain point Object #2 re-appears trailing short length of string. Probably a daft idea, but it might throw up some workable ideas from someone else.