Bought the original Teddy for my daughter in 1986.  He stopped working & I got rid of him.  Just found 3 of the books without the tapes. Went to eBay 7 bought another Teddy to give to my grandson & need to find the cassettes to go with the books.  Need help finding the cassettes for 'The Missing Princess', 'Grubby's Romance', and 'One More Spot'
Can anyone help me?

I suggest checking out ebay, it's a really good to place, to find things, such as that.

Ah, Teddy.  Not only the first widely-popular animatronic toy, but probably the first hackable animatronic.

If you're able to find someone with the tapes, you may be able to record them to either another tape (info here), or to the computer.  Stereo .WAV or some lossless format is probably the best way to go; judging from this page, it shouldn't be too hard to take the audio data (the only reason I suggest the computer is that you could clean it up on the computer if there were problems with a tape-to-tape dub) and play it back into a tape recorder.

As long as you use stereo (not Joint Stereo) encoding, the MP3 encoder should be able to sort out what's going on on the PPM track that controls the animation; from what I saw on the web, I doubt an exact match on the frequency matters, and MP3 should come close enough to a square wave for for the sorts of timescales being talked about.  So even if the cassette player has failed after a few years in storage, you should be able to hook up a cheap thumbdrive-style MP3 player to it and make it work.

Then there's the guys who hacked Teddy to work with Twitter (!).  The original website's gone (here's the wayback machine's cache, but it doesn't have the source code), but if that link doesn't have it, this link should have video of the results.  Insane, but awesome.

(Hey, anyone actually do this?  Did you document it?  Hook the thing up to an Arduino?  Got a copy of that source code floating around?  Most of the Teddy Ruxpin hacking pages I found were old.  If you've got current hacks/data/etc, link 'em here.  Yes, even if this thread's a few years old when you find it -- we've got memories like elephants on this message board.  Ever record Black Sabbath's "Iron Man" (or Eminem's "Without Me"!) on one track of a and throw down some (in)appropriate motion control on the other track, but never thought anyone would be interested in an MP3 of the results?  Guess what, we're interested now!)