"Harry, I'm going to let you in on a little secret. Every day, once a day, give yourself a present. Don't plan it, don't wait for it, just let it happen. Could be a new shirt at the men's store, a catnap in your office chair, or two cups of good, hot, black coffee. Like this."  -Dale Cooper

Not sure about the actor playing the Giant, BUT, the actor playing the Elderly Waiter (Hank Worden) had already died by that time. The two rarely appear without each other.

There's also some evidence that the Giant is Cooper's familiar, or perhaps guardian spirit, but he does not need to appear until Cooper is near death in episode 2.01. In FWWM, Cooper's appearances are limited anyhow. He could theoretically have appeared in the final scene, with Laura and the White Angel in the White Lodge, but well, it didn't happen apparently...

Carel would have loved to have been in FWWM, but he was not asked.

 
Carel Interview

 Evidentally you don't understand the term "familiar" in the occult sense, which is what Mike meant when he said that BOB was his familiar. Here it is from wikipedia ; 

Familiar spirit

 I don't think that is the sense in which Mike meant that BOB was his "familiar" at all.  There is nothing to suggest that BOB appeared to Mike in animal or owl form... in fact, the tattoo connection seems to disprove this.

This addition to wiki, it seems, is conjecture and should be flagged.

In what sense is Mike more powerful than BOB?

We see BOB inhabit people and commit murder and rape (garmonbozia), but what do we actually see Mike do? Apart from, I suppose, inhabiting Philip Gerard.