Help! My Boyfriend Is 5 Years Older Than Me And Won’t Stop Making References to Early 2000s Flash Animations I Don’t Understand

It all started when I told him to slow down while driving because the speed limit was 55 and he started saying “Schfifty-Five” a lot while calling me a little girl and saying that his IQ was also Schfifty-Five. Suddenly he’s giggling like a small child and I have no idea what’s so funny.