"Okey-dokey, Flash!" Bart chimed, only to have an extra shadow looming over him. Bart craned his head up (and up and up and up) and almost all the way over to look up at Batman with his jaw dropping a little. "MEEP-MEEP!" He cried, Roadrunner-esque, and tore off to put the Bat Signal between himself and Batman (he wasn't scared. Not at all. Nope. Not him). But whatever courage he may have lost from the Batman intimidation was regained when his Grampa stood up for him. Bart peeked his head up over the top of the Bat Signal to stick his tongue out at Batman. So there.
But that's when Bart tuned into the rest of the conversation and heard The Flash speaking. He said that Bart was claiming to be his grandson. Bart opened his mouth to protest, "But I AM your grandson. You and Grandma Iris had twins- my Dad, Don and my Aunt Dawn- and then Aunt Dawn had my cousin Jenni and my Dad married my mom Melanie Thaw--..." Bart suddenly stopped short and looked like he might have swallowed a goldfish. "Uh. My mom... my mom Melanie. And they had me." He said, slowing down and looking towards his enormous, yellow-booted feet.
But his head picked up and eyes widened when Barry said be believed him-- "You do?" He asked in shock, amazement and more than a little excitement. Was it clear yet that Bart adored his grandfather?