I think my dog ate a chocolate bunny!

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Here's a good resource for you.  Bookmark it for future reference.  http://www.aspca.org/pet-care/poison-control/people-foods.aspx  

The Xylitol mentioned on the site above is more dangerous than chocolate.  In fact, it is as dangerous as rat poison.

It is a good sweetner for humans and is in a growing number of products - liquid/chewable medications, breath mints, candy, gum, mouthwash, toothpaste, cookies, cupcakes, etc.  You should even double-check chewable and liquid prescriptions for dogs. 

Just one little Xylitol breath mint can kill a small dog.  A pack of Xylitol gum can kill a large dog. 

If you even suspect that your dog (any size) got into some Xylitol, it is grounds for an ASAP emergency trip to the vet.  Do NOT wait!! 

Chocolate has a component called theobromide -- that's the stuff that causes the problem.  When chocolate is processed in the digestive tract, it turns into a substance in the liver very like cocaine (yeah, I really DO mean **cocaine**).

The darker the chocolate the worse it is.  The 'better' the chocolate the worse it is (because better chocolate tends to have less wax and fillers).  Bitter baking chocolate is THE worst -- but the stuff in milk chocolate (the milk, sugar, wax) can make the dog sick on its own.

Part of the problem is that it's VERY individual.  I hate to see people just go by a "chart" because MUCH can depend on the state of the dog's liver currently -- my pug got into a small amount of Hershey's kisses two Christmas's ago -- she was in agony for HOURS (I was honestly terrified she'd have a heart attack she was so hyper). 

 BUT afterward  it left her liver pretty compromised and I had to do some serious detoxing to get her back to full health.  It wasn't anything that "showed" other than on bloodwork -- but a compromised liver can make a lot of other things 'worse' rather than having it's own definable effect. 

Pralines?  Dogs do NOT digest nuts well (and frankly that goes for peanut butter too).  They mostly LOVE nuts -- but the oil in tree nuts, particularly, can cause some SEVERE stuff -- even up to and including pancreatitis.