Well, it's a shock when a cat does this sort of thing, I know, Debra.
Flatty, the last of my remaining 3 from my previous home, is strangely excitable at unpredictable times, too. He was an adult stray (or maybe an extremely neglected & unsocialized cat) when we gained the pleasure of his company.
He is still very dependent, often becoming anxious when he senses I'm about to leave for work, etc. But sometimes I honestly don't understand his reactions. He'll be hanging around the clothesline, say, when I'm hanging out clothes. He'll show that he wants to "participate" in the activity by his interest & playful threats to jump in the clothes basket, etc. THEN, when I try to walk away when I'm finished, he'll pounce (!), attack my legs as I'm walking back into the house! It's as though he wants to keep me engaged, or something ... He's VERY excitable! Sometimes, seriously, I've wondered if he believed I was another cat & treated me as such!