OMG, I'd die of happiness if I saw a sub-boss Lulu. She'd be great with Veigar! I can actually imagine a pretty epic game with the five of them.
Hecarim charges to initiate. Lulu polymorphs him into a squirrel and glares at him menacingly as he cowers. Miss Fortune tries to blast Lulu away, but her shield saves her and she blasts back with a glitterlance. Sona save them all from CC domination as they retreat whilst Lulu laughs in triumph. "You nosy dewdrops don't have what it takes to stop my Vivi!"
Meanwhile, Veigar watches the battle from his evil throne room on his epic flatscreen of evil and facepalms at the mention of her pet-name "Vivi."