"I'm just saying" is a trope. It's certainly not as tropey as what you see in the second joke. The humor in the first is in the pure ridiculousness of compari

"I'm just saying" is a trope. It's certainly not as tropey as what you see in the second joke. The humor in the first is in the pure ridiculousness of comparing the height with what it would be on a globe, which is why it's written with the adoption of the sort of persona that would follow up a comment with "I'm just saying."