Preheat oven to 200°F. Set a rack in a 4-sided sheet pan and put in oven. Mince and mash garlic with ¾ teaspoon salt, then whisk together with water, eggs, and sesame oil. Whisk in flour until smooth. Stir in scallions, bell pepper, and shrimp.
Heat 1 tablespoon oil in a 12-inch nonstick skillet over medium-high heat until hot. Stir batter, then cook pancakes in batches of 4 (2 tablespoons each, with some vegetables and 1 or 2 pieces shrimp), pressing down lightly with a large spatula to flatten and evenly distribute vegetables, turning once, until golden and cooked through, 3 to 5 minutes per batch. Drain on paper towels, then transfer to rack in oven to keep warm. Add oil to skillet between batches as needed.