I'm too afraid to introduce them! My dog (Zoey) is part border collie, so she chases anything that moves... especially squirrels. And my lil chinchin looks too much like a squirrel... I'm also still getting to know her since we just got her from the shelter about a month ago. Cheech (my chinchilla) is too old and slow and blind for me to feel comfortable letting him be around the dog.
Also, Zoey was obviously a mother before we got her. She treats her stuffed toys like babies, and picks them up gently. So I'm also afraid she might try to pick him up and accidentally hurt him. They're both so sweet though, I'm sure they'd get along great if they were around the same size! I just don't want anything to happen... especially because of how fragile chinchillas are.