Larry first encounters Jack Jackson at a Hair Dependents Anonymous meeting.

Like Larry, Jack Jackson has an animal living in his hair.  In Jackson's case a snake named Sam has taken up residence in his beard.

It's clear that Jackson is privy to a world of animal conspiracy that Larry is only beginning to understand.  It's also clear that Jackson and Dr. Sachtler have crossed paths before.

Despite being homeless (and maybe a little crazy) Jackson is clearly a powerful ally.