As for the problem for Smart Hulk already existing at the beginning of Avengers: Endgame during the movie’s main shoot, this was rectified by filming the diner scene during reshoots where Bruce Banner explains to Captain America, Black Widow and Ant-Man how in the five years between The Decimation and the time heist, he worked in the gamma lab for 18 months to fuse the brains and the brawn together, resulting in the birth of Smart Hulk, the best of both worlds.