Sim automatically went to 'cheer up' their partner after 'playing in bed'?

I'm so confused! I've been playing the Sims 1 literally since its release in 2000 (yes I'm getting old) and have never seen this:

I was playing the Mashuga family, as you do, and I had Frankie and Sylvia Marie play in the love bed, as you do.

Anyway, immediately after said 'play in bed' was over, Frankie automatically went to Sylvia Marie to 'cheer her up', to which she responded with a... Giggle?!

I've never seen this ever lol. Free will was off, both of them were in a great mood and their relationship bars are both at 100.

Any ideas haha?!