Thank goodness my almost 2 year-old wasn't sitting on ME when he uttered those words, but my poor husband, he was rather shocked by the apparent comparison.
We were just at Sea World a couple weeks ago meeting my girlfriend of 30+ years. Nine of us (my friend and her three kids, me and my three kids, plus my nephew) climbed on the Shamu statue together and had our photo taken. Everyone except my almost 2 year-old cooperated. Considering his resistance on the statue, it surprises me that he would pretend to be "riding Shamu" again with his dad.
Just a side note, my friend and I met when I was two years old...so 30+ years doesn't age me quite as much as you might think :)