Seth MacFarlane: No Plan B for Tom Brady's Sperm

Seth McFarlane's go-to set o' gonads belong to one Tom Brady ... as we learned when Seth dropped some "Ted 2" trivia on us.

The Patriots QB turned in an Oscar-worthy performance in Seth's hit movie last year. If you haven't seen it, the role centered around Brady's balls ... and NOT the deflategate ones.

We got Seth outside the Palm in Bev Hills, and asked who would've stepped in if Brady wasn't available -- after all, New England has no shortage of sports heroes. Gronk, Bird, Big Papi???

Seth did eventually offer up one possible backup plan, but God ... we hope he was kidding.

Seriously, he was kidding. Right?