Merida's lines can get quite long! We were at WDW a couple weeks ago and went straight to Merida's M&G after the opening show (her first set began at 9:15am with a 9am opening, which I think is her typical schedule). So, we waited about 15 minutes, but I grabbed some pastries for us from a nearby cart so it didn't feel like a long time at all. Plus the M&G lines tend to build throughout the day, so we committed to going there at rope drop.