The boots
 

Bert, 80, always wanted a pair of authentic cowboy boots. So, seeing some on sale, he bought them and wore them home:

Walking proudly, he sauntered into the kitchen and said to his wife. “Notice anything different about me?”

Margaret, 75, looked him over.
“Nope.”

Frustrated, Bert stormed off into the bathroom, undressed and walked back into the kitchen completely naked except for the boots.

Again he asked Margaret, a little louder this time. “Notice anything different NOW?”

Margaret looked up and said in her best deadpan. “Bert, what’s different? It’s hanging down today, it was hanging down yesterday, it’ll be hanging down again tomorrow.”

Furious, Bert yelled. “AND DO YOU KNOW WHY IT’S HANGING DOWN, MARGARET?”

“Nope. Not a clue.” She replied.

“IT’S HANGING DOWN, BECAUSE IT’S LOOKING AT MY NEW BOOTS!!”

Without missing a beat, Margaret replied. “Shoulda bought a hat, Bert! Shoulda bought a hat.”