Did I not get the memo or toddler goes crazy by 18 months??

Today was horrible, one of the worst behaved days from LO up to date. He just turned 18 months 1.5 weeks ago and we literally just got back from his 18 month well visit. Funny thing is my friend who has the same age baby (hers is 3 days older than LO), and she was just complaining about the same thing.

Today we went out to do some shopping (Tax-free day where we are). He whined to get held, not by his dad, but by me! He usually likes to walk around on his own but no, he needs to be held today BY ME. ?????? If I hand him to daddy he'd cry, scream and struggle. If I put him down and ask him to walk he'd cry, scream and struggle. Then he took husband's wallet when he was paying for something, and when husband got it back from him, he cried and cried all the way from the mall to where our car is! DH had to carry this crazy child as if we were these clueless parents who doesn't know what we were doing (maybe we were, but this hasn't happened before in THIS magnitude). He won't let us strap him down in the car and he'd cry hysterically if we attempt to do that! And he slept well last night and napped 2.5-3 hours so I can not blame exhaustion!

What is going on? Did I not get the memo? Is this happening to you too?