“Family Guy” is officially 18 years old — kind of. While the series premiered 18 years ago, it has only had 15 seasons so far. Although the series first premiered on Jan. 31, 1999, it lasted only two seasons before being canceled by Fox in 2000. The network then produced a third season in 2001 which ran until 2003 when Fox once again canceled the show.

It wasn’t until two years later that Fox would again bring the show back for its fourth season, which has continued to today’s 15th season. In honor of the 18th anniversary of the 1999 premiere of “Family Guy,” here are 18 things you may not have known about the hit series:

1. Stewie’s voice is based on Rex Harrison. While Brian’s voice is basically Seth MacFarlane’s regular speaking voice, his best friend Stewie’s voice is based on actor Rex Harrison.

Photo: Fox

2. Lacey Chabert voiced Meg. During the first season and part of the second season, Meg was voiced by actress Lacey Chabert of “Mean Girls” fame. Chabert left the show in order to focus on school and other projects, and the role then went to Mila Kunis.

3. Lois was supposed to have blonde hair. During pre-production of the series, the creative team wanted to make Lois a blonde. The team eventually decided on her being a redhead, but her pre-production days are why Chris has the same blonde hair color she would have had.

4. The show was originally conceived as “MADtv” shorts. Similar to “The Simpsons” and “The Tracey Ullman Show,” MacFarlane originally created the Griffin family as characters that would appear in animated shorts on “MADtv.”

5. The series owes some thanks to “King of the Hill.” When MacFarlane first pitched “Family Guy” to Fox, Mike Judge had just signed a deal for “King of the Hill.” Fox didn’t want to take on two cartoons so the network said no. A year later, MacFarlane tried again, and thanks to “King of the Hill” finding success on Fox, the network picked up “Family Guy.”

6. William H. Macy auditioned for Brian. While Brian’s voice is now iconic, the role could have been played by William H. Macy.

7. Rachael MacFarlane never voiced Meg. Although rumors have claimed Seth MacFarlane’s sister voiced Meg in the pilot episode, MacFarlane herself debunked the claim, saying it never happened.

8. Cree Summer was supposed to voice Meg. Cree Summer (“A Different World,” “Rugrats”) was supposed to be the voice of Meg but was fired before the pilot.

9. Seth MacFarlane says the cutaway gags are the hardest to write. “Family Guy” is infamous for its cutaway gags, which some see as lazy, but according to MacFarlane, they’re the most difficult parts to write.

10. Alex Borstein almost lost her job as Lois. After the pilot, Fox wanted to get rid of Borstein, the voice of Lois, and head in a new direction. “I had to fight to keep my job. I had to re-audition for it,” Borstein said.

11. George Lucas gave his blessing. “Family Guy” has done three “Star Wars” episodes which all started with Fox clearing “Star Wars” jokes with Lucas. The director was fine with the jokes, as long as the characters looked exactly like they did in the films.

12. The voice of Chris is based on Buffalo Bill. Chris’ voice is based on the famous “Silence of the Lambs” character, Buffalo Bill, who Chris actually portrayed in one episode.

13. The giant chicken has a name. Peter’s epic fights with the giant chicken have become a long-running gag on the series, but during a Season 5 episode, many fans may have missed that the chicken’s name is Ernie.

14. Seth MacFarlane’s favorite episode is “Road to the Multiverse.” While some “Family Guy” fans miss the old days of the series, MacFarlane’s favorite episode was the Season 8 episode, “Road to the Multiverse.”

15. Episode names were originally based on 1940s radio mystery shows. The first season of the series features episode titles such as “Death Has a Shadow,” “I Never Met the Dead Man” and “Chitty Chitty Death Bang.” This was due to the fact that the team wanted all the episodes to have death in the title, but it proved to difficult as the series went on.

16. Homer Simpson has appeared in two episodes. “Family Guy” has made a ton of “Simpsons” jokes during its 15 seasons but Homer Simpson and his real voice actor, Dan Castellaneta, have only appeared twice.

17. There is no real Quahog, Rhode Island. While the series takes place in Rhode Island, there is no town called Quahog in real life. Instead, quahog is the name for a hard clam.

18. Carrie Fisher was the voice of Angela. Up until her death in 2016, Carrie Fisher of “Star Wars” fame was the voice of Peter’s boss, Angela.