I'm more of a lurker than a poster around here, and I surfed all around the day after the vax comment on American Dad - I thought for sure it'd be mentioned before now! I did a double take at it too, so funny! I also caught the Family Guy "no thanks, I'm full" - I retold the whole thing to Dh, who missed it, and he even thought it was funny in the retelling! Makes me like the shows all the more - they're sort of a guilty pleasure for me and these things give me more of an excuse to watch!
Oh, and Stewie attacking the nursing mom at the park, sneaking into Lois's room at night with the breast pump, and Peter nursing Stewie are all classic moments! I also remember Lois wearing Stewie (in a bjorn type carrier, I think) in an episode (I think they're at a pool?).