The chemical in chocolate that's toxic to cats (& dogs) is theobromine.
Milk chocolate contains the least amount of the chemical, dark chocolate
more, & bitter/baking chocolate contains the most.

Although I personally wouldn't feed it to my cats, minute amounts of milk
chocolate are not likely to cause any symptoms.  Since pudding may have milk
chocolate in it - or maybe even chocolate flavoring Vs. real chocolate? - &
in small amounts, that's probably the explanation.

In one of Peter Gethers' books about his (late) cat Norton, he told of a
restaurant owner who set a dish of chocolate ice cream out for Norton on a
fairly regular basis, yet Norton never showed any ill effects.  The amount
of theobromine that was in each serving was obviously not enough to have an
effect.

Larger amounts, esp. of darker chocolate can prove to be toxic, incl. fatal,
though.

Cathy

--
"Staccato signals of constant information..."
("The Boy in the Bubble")  Paul Simon

circa Tue, 09 Mar 2004 21:03:58 -0800, in rec.pets.cats.health+behav,
Dennis Carr (ke6isf@spamcop.net) said,

It isn't deadly in *minute* amounts- toxicity varies by weight of the
animal and the type of chocolate consumed (cocoa and baker's
chocolate are the worst). With that said, cats are *not* immune to
chocolate toxicity; in fact, due to their smaller size, they're
usually more susceptible than dogs. Chocolate pudding doesn't really
have a lot of chocolate in it, which is probably why the cat in
question was able to eat it. Camille has been known to lick the top
off of part of a pan of brownies if I let them cool on top of the
stove, so now I have to let them cool in the oven instead.
Fortunately, she has (knock wood) not gotten sick from it.

Theobromine, which is quite different than theophylline, is what is
in chocolate. ;-)

Just found a link:
http://petplace.netscape.com/articles/artShow.asp?artID=602

Laura

The acute lethal dosage of theobromine in cats is ~80-150 mg/kg.  That
translates into ~320-600 mg for an average 4 kg (8.8 lb) cat.  A cat would
have to eat at least one ounce of baking chocolate or 8-10 ounces of milk
chocolate to ingest a toxic dose.

Baking chocolate contains ~400 mg/oz of theobromine;
Dark chocolate:  ~130-150 mg/oz;
Semisweet chocolate: ~140 mg/oz
Milk chocolate: ~40-60 mg/oz;
White chocolate: ~0.25 mg/oz

The toxic ingredient in chocolate is theobromine - not theophylline.
Theophylline is in the same family (methylxanthine) as theobromine and is
also toxic to cats at higher doses than theobromine.  Theophylline is used
at low dosages as a very effective bronchodilator in cats with bronchitis
and asthma.

Chocolate also contains caffine (in lesser amounts than theobromine), which
is also a methylxanthine and toxic to cats.

If I were you, I wouldn't feed chocolate to my cat.  There are plenty of
other treats you can give a cat that she would enjoy much more.

Phil

(...)

A trivial addition to the other replies - theophylline is a component
of tea, so if your cat drinks the odd cuppa, only then might you be
interested in that ingredient...!

Steve.

You are typical of today's push-button knee-jerk liberal liars. You
just won't rest until you've stirred everybody and everything up and
you've PCed everything in your path. You're the same stupid idiots who
tell us not to feed our cats fish or not to give them milk. You are
also the same ones who are telling us now that it's all right for a
man to marry another man. All quite natural, you see. You just can't
wait to reshape society in your own narcissistic image.
Don't come in here with your PC trash again. I will be watching out
for you and you will be constantly and immediately rebutted to the
highest degree. Not everyone is a Jerry Springer Pro wrestling sitcom
loving zombie, prickweed. We won't quit giving our pets treats anymore
than we could be duped into voting for Hillary Clinton. We know who
you are and we know what you do. Keep away.

                        IBen