Sleep regression?

Is there a sleep regression in the 3rd year? My 3 year old this weekend decided he didn’t need to nap. Saturday he didn’t nap at all and was surprisingly still in a good mood the rest of the day and slept through the night. Then Sunday he fought me for a nap but eventually fell asleep but woke up at 3 am asking for me. When I went in there he asked to count his cars on his poster. I said no it’s night time so he did go back to sleep. I remembered my OB saying something about him probably going through a regression at some point probably before baby. So it just kind of clicked that could be what it is. But wasn’t sure if it’s a real thing