My life as a math nerd:

Me: did you know that any natural number equal to one mod 4 can be written as the sum of two squares?

Them: what about nine?

Me (not in front of reference material): <stammers>

Me (12 hours later): OK, any PRIME equal to one mod 4. For example, 13 = 2^2 + 3^2, 17 = 1^2 + 4^2, 29 = 2^2 + 5^2, etc.

Them: 👍