The ‘Full House’ star shared an adorable slideshow of his son through the years, as he prepares to send his little boy off to school!

Have mercy! John Stamos‘ son Billy, 3, is growing up so fast, and the 58-year-old Full House star can’t believe it! John posted a slideshow of his only child through the years, as the little one prepares for his first day of school on Wednesday September 8. John’s “mini-me” couldn’t look happier to start school, even if his dad got a little choked up at how quickly his son is growing up!

With the slideshow set to The Beach Boys’ classic tune “When I Grow Up (To Be A Man),” John shared photos of Billy from infancy to leaving for his first day of school. All the photos were adorable, and the little one looked just like his dad. Especially with his hair grown out and combed, Billy looked like a much younger version of John’s iconic Full House character: Uncle Jesse. In the last photo, Billy smiled for the sweet photo. He rocked a blue button-down Hawaiian shirt with white flowers. He also sported blue shorts and white sneakers, and he looked prepared for school with an awesome Spider-Man lunchbox. John couldn’t hold his emotion back. “First day of school. I’m not crying, you are,” he wrote in the caption. 

John Stamos, 58, shared an adorable video of his three-year-old son Billy on Wednesday. (Shutterstock)

Billy is John’s only child. He had the boy with his wife Caitlin McHugh35, in 2018. John gushed over Billy to HollywoodLife in January 2020, especially about the youngster starting school. “I’ll tell you this. The thing what happened today is, we had to go look at preschools, and I walked into the first one, I started bawling my head off” he said.

Billy is John’s only son with his wife Caitlin McHugh, 35. (Shutterstock)

Earlier this year, John starred in the Disney+ series Big Shot, where he earned the praise of his co-star Yvette Nicole Brown. “If there’s ever a reason to tune into anything, it’s John Stamos!” she told HollywoodLife in an April interview.  Back in March, John reminisced on hiFull House days in the 90s, sharing a photo of Mary Kate and Ashley Olsen at DisneyLand. He also celebrated their sister Elizabeth Olsen and her success with WandaVision by looking back on what it was like to have her on the set, even though she wasn’t on Full House.