I do. I tested their object
permanence with a RUBBER duck,
The Big Bang Theory Season 12, Episode 17
If you really want to help,
put on a RUBBER glove,
The Big Bang Theory Season 11, Episode 16
Like when it turns out
she's made of RUBBER,
The Big Bang Theory Season 7, Episode 20
Not the brush part.
Just the little RUBBER thing...
The Big Bang Theory Season 4, Episode 6
...and glued a big-eyed RUBBER alien mask
to the outside of my window.
The Big Bang Theory Season 6, Episode 2