old yeast...underpitched?

I just brewed up a 5 gallon batch of Janet's Brown ale and had an OG of 1.065.

I thought I would try using the Smackpack Wyeast Pacman from Rogue that I got a couple months ago. I didn't realize it was actually really old. It was a limited release made available January though March of 2010 so it could actually be year old!

I did a 2 liter starter on a stirplate, and it fermented out like normal...though I will have to say that when I cold crashed it, there wasn't a ton of yeast on the bottom, and it looked nice an creamy white.

I've never pitched yeast this old...or I guess since I did a starter with it, this little. Any ideas of what I can expect? I usually pitch a really good amount of healthy yeast. I guess it isn't so much old yeast as it is a small amount?

That's hardly "old Yeast" especially since you made a starter. If you make a starter, then the age of a yeast isn't really an issue.

Bobby M did a test on year old stored yeast here; https://www.homebrewtalk.com/f13/testing-limits-yeast-viability-126707/

And my LHBS cells outdated tubes and packs of yeast dirt cheap 2-3 dollars each and I usually grab a couple tubes of belgian or other interesting yeast when I am there and shove it in my fridge. and I have never had a problem with one of those tubes.

I usually make a starter but I once pitched a year old tube of Belgian High Gravity yeast directly into a 2.5 gallon batch of a Belgian Dark Strong, and after about 4 days it took off beautifully.
The purpose of a starter is to reproduce any viable cells in a batch of yeast....that;s how we can grow a starter form the dregs in a bottle of beer incrementally...and that beer may be months old.

Even if you have a few still living cells, you can grow them....That's how we can harvest a huge starter (incrementally) from the dregs in a bottle of some commercial beers. You take those few living cells and grow them into more.

You did the right thing. I think you will be fine.

That is a delicious beer!!! Loved it the first time I brewed it. Cant wait to brew it again as an all grain recipe.

Well, I guess Pacman is some pretty serious yeast. 4 days later at 62F it fermented down to 1.015...right on target.