Worlds of Wonders made their Teddy Ruxpin bear mainly from 1985 to 1987.  
They all took 4 C type batteries on look similar even through there were
modifications made to them internally and to a lesser degree externally.
Within these Teddys, were what is referred to as the 1st, 2nd & 3rd generation
Teddy Ruxpin bears.  All of these Teddy Ruxpin bears were compatible with
the accessory items put out at intervals by Worlds of Wonder.  They were the
answer box, the projector and the Grubby toy.  These are all run through the
Teddy output on the back of Teddy under the battery door.  All these
accessories including Grubby will not work without a working Teddy Ruxpin.
The projector will show the slides but there will be no story without Teddy.  
After Teddy Ruxpin was released, it became apparent that Teddy was prone to
various conditions causing him to fall into a coma and not work.  Worlds of
Wonder was soon swamped with Teddy Ruxpin repairs in their Grundo
hospital.  These repairs were expensive and adding repair expenses to the high
purchase price of the toys in the '80's, Teddy Ruxpin was a very expensive
investment for parents.  Unfortunately, the target age for this toy was not an age
when I child can handle a delicate electronic toy without breaking it.

By the time Grubby came out a year after Teddy, parents had already spent
alot of money keeping Teddy going.  Grubby does NOTHING without a
working Teddy.  The batteries that go in Grubby actually will only power
Grubby when signals come from Teddy.  Parents became somewhat
disillusioned with the toys and WOW started failing financially.  Changes were
made to Teddy Ruxpin in the next few years in an effort to improve Teddy's
reliability and decrease costs.  That created the different generations of Teddy
Ruxpin's by WOW.  The company went bankrupt and ceased production in the
late '80's.  In 1992, Playskool took over Teddy Ruxpin production.  Some of
the early ones produced still had WOW patents listed on the boxes and tags
leading to confusion over which Teddy you have and who made it.  The
Playskoll versions were smaller.  The vest is sewn in place instead of being
separate like the first Teddy. Although they used the same stories, they were on
a small cartridge instead of a cassette tape.  The original Teddy took 4 "C"
batteries and the newer Playskool version takes 4 "AA" batteries.  The books
that accompanied these "cartridges" tended to be paperbacks instead of
hardcover like the original Teddy cassette tape books.  The Playskool bears do
not work with anything accessory items and do not connect to Grubby.  Their
insides are totally different from WOW bears and not easy to fix.  The
cartridge player in the back had no door on it and quickly got so dirty that it no
longer worked.  The facial features were all connected by pulley belts that
stretched and slipped.  Needless to say these were not made long and never
really caught on even though there is quite a few of these are still around, most
of them inoperable.  The third attempt to bring back Teddy Ruxpin was by YES
entertainment in 1998.  These were marketed to be able to work with your
computer and with a VHS tape where Teddy talked with the Video tape.  The
video ability was operated with an "optional" video pack. Obviously the
computer system available in 1998 is much different from today's systems, so
even if you purchased a working one today, it would not work with today's
computers.  I am not sure how well they actually worked with a computer in
1998.  This bear is the same size as the Playskool version but without the
orange body/tan vest look of the earlier version.  This one is wearing a red/blue
jumpsuit body with a yellow belt.  None of the clothes are removable, in fact
all the clothes available for Teddy Ruxpin were designed to fit the original
WOW bears.

In 2006 Backpack toys released the digital version of Teddy Ruxpin that is
completely digitally.  It is a small bear about the size of the Playskool and Yes
Entertainment bear.  It does not in anyway connect to Grubby and uses it's own
digital cartridges.  Like the other post Worlds of wonder releases, it never
captures the look or magic of the original Teddy Ruxpin and Grubby.
World of Wonder
Teddy Ruxpin
1992 Playskool
Teddy Ruxpin
1998 YES
Teddy Ruxpin
2006 Backpack
Toys Teddy Ruxpin