Certainly! Here's a test case generator for the given problem statement "Online Quizu System":

```python
import random
import string

def random_string(length):
    return ''.join(random.choices(string.ascii_uppercase + string.ascii_lowercase + string.digits, k=length))

def generate_test_case():
    # Generate random values for M and N within the given constraints
    M = random.randint(1, 100)   # Number of players
    N = random.randint(1, 100)   # Number of problems

    # Generate random delays for each player
    D = [random.randint(0, 100) for _ in range(M)]

    test_case = []
    test_case.append(f"{M} {N}")
    test_case.append(" ".join(map(str, D)))

    for _ in range(N):
        # Number of players that submitted an answer for this problem
        L = random.randint(0, M)
        submissions = []
        for _ in range(L):
            P = random.randint(0, M - 1)  # Player ID
            T = random.randint(0, 19999)  # Time elapsed
            A = random_string(random.randint(1, 9))  # Player's answer
            submissions.append(f"{P} {T} {A}")
        test_case.append(f"{L}")
        test_case.extend(submissions)

    return "\n".join(test_case)

def generate_multiple_test_cases(num_cases):
    test_cases = []
    for _ in range(num_cases):
        test_cases.append(generate_test_case())
        test_cases.append("0 0")  # To mark the end of the input
    return "\n\n".join(test_cases)

if __name__ == "__main__":
    num_cases = 5  # Number of test cases to generate
    test_cases = generate_multiple_test_cases(num_cases)
    print(test_cases)
```

This code will generate multiple test cases for the described problem. Each test case includes:
1. Random values for `M` and `N`.
2. Random delays for each player.
3. Random submissions for each problem, following the given format.

Each test case ends with `0 0` to mark the end of input, as specified in the problem statement. The function `generate_multiple_test_cases` allows you to specify how many test cases you want to generate and outputs them in the required format.