Just a bit more... I noticed that OTHER "Spongy Moves" work fine.  So, just my luck, I seemed to have picked the one motion "Box Falling" that doesn't seem to work with the linking.  Must be a bug with that one prop motion.

Secondly.. Just wanted to mention that if those Elastic Motions do indeed have un-editable Opacity settings at the beginning (Entrance) and end (Exit) stage... that's fine.  That makes sense... HOWEVER... 
I would expect the Opacity reading at the top of the screen to genuinely reflect the actual Opacity at each given time frame, when you have an object selected.  If not, then I consider that to be a bug in the program that should be fixed.  

I'm not sure if Opacity bug is relating to "Linked" objects or "Elastic Motions".  ¯\_(ツ)_/¯

I'm following along with a beginner Tutorial Course from David Arandle (great course BTW)... anyway... I'm Linking a Character to a simple icon Prop.  Then I'm applying an Entrance elastic motion to the Prop. (to make the character also follow along with the elastic motion).

I notice that when I play the animation... for the first 2 or 3 frames, the Prop icon is invisible...  Even though, when I click on the Prop (and I'm in the first frame) the Opacity shows as "100".  The Opacity continues to show as "100" even though it's definitely doing a gradual fade within the first 3 frames. 

Now normally, I know, you would want to make that Prop invisible.  But just for this experiment... I wanted to have the Prop be totally and completely visible (Opacity 100) throughout the entire animation.  But it seems like that doesn't work.  It's almost like the Entrance motion has an automatic Opacity setting that can't be overridden.  Is that true?  Is that how these Entrance motions work?

Also... I tried to Link a G3 character to a Prop and then use a " Spongy Moves" elastic motion... but it failed to work at all.  The Character just stayed in one spot, while the Prop and Elastic Motion played it's animation.  It seemed the Link failed.  Are those Elastic Motions somehow "different" and not able to work with a Linked character?  Thanks for any insights you can give.  I appreciate the help.