Childhoodgasm

When you relive or reminisce about your childhood emotionally or mentally, usually triggered by something physically.

Or

To achieve pleasure or content in later life with or about something that would've made you happy as a child.

When we saw the swings at the park yesterday, we had a complete childhoodgasm.

I was watching The Aristocats the other day, and I realized I haven't seen it since I was 11. It gave me the biggest childhoodgasm.