I recently read an entry in the Star Trek Encyclopedia which noted that there were a lot of little 'in-jokes' on the Enterprise-D's Master Display in Engineering, including a Porsche. One of the most famous was a hamster wheel which supposedly powered the Enterprise-D (if you thought it was the warp core, you were wrong!). My question is then: do we ever see this hamster wheel on the Master Display in a TNG episode or Generations?
Took some searching, but I finally found him...
Thank Cracked for the image
Thanks Hypnosifl to for the comment:
The image is apparently from Star Trek The Tour, see Joel Zink's photo gallery here which has an identical image. So, this doesn't really answer the original question about whether it was ever seen on TNG.
So it appears this is not actually from an episode of TNG, but still proof perhaps that it exists.
This is an image from episode 11001001 (1x15) in which Picard and Riker initiate self destruct in engineering. Frame grab at 33mins 14 seconds.
Now admittedly this is season 1, but you can clearly see that is does NOT match the "The Tour" image in Daft's answer, and does not show the wheel.
I can't find the hamster wheel, but you can see a blurry version of some of the other gags in the original version of "The Mind's Eye" (4x24), but these were digitally removed in the 1080p remastered version.
Here's a gif showing the difference (low quality due to gif size limit): https://i.stack.imgur.com/W6juc.gif
Here's the original SD release in full detail:
Gags removed: a "slippery when wet" sign, an outline of a person and child, and a handicap sign. Here's the closeups:
You can see some of those in detail in this fan photo of the set I found online here.
In the 1080p remastered version of this episode, you can see that they've been removed.