What a fun topic this is.
When my son was 3 (he's 32 now) he was lying on the bed with his grandma. Now, my mom was deeply & heavily wrinkled (too much sun & smoking). So my son is stroking gramma's face & says, "Grammy, you need to iron your face".
Even though she was self-conscious about her wrinkles my mom thought that was one of the funniest things she'd ever heard.