'Family Guy' -- Brian Griffin Returns ... Back From the Dead

Jesus Christ ain't got nothing on Brian the dog ... as "Family Guy" brought him back from the dead on last night's episode -- 3 weeks after he was left for roadkill.

Here's how Brian Griffin was resurrected -- Stewie cries to a mall Santa that he wants his best friend back -- and then through a wrinkle in the time-space continuum ... steals his broken time machine from another version of himself ... but before it was broken.

Yeah ... time travel is confusing.

Blah, blah, blah ... Stewie goes back in time, and pushes Brian out of the way of the car that ran him over.

After the episode ... Seth MacFarlane tweeted: "And thus endeth our warm, fuzzy holiday lesson: Never take those you love for granted, for they can be gone in a flash."

Whatever. All we know is Brian's back ... all is right again.