You Are Neither Old Enough Nor Young Enough to Enter Legoland Alone
Children must be accompanied by adults and adults must be accompanied by children.
Here are the admission rules for Toronto's Legoland:
Please note: Children 17 and under must be accompanied by an adult supervisor 18 years of age or older. Adults (18+) will not be admitted without a child, with the exception of Adult Only Nights.
So when you are 17 and 364 days old, you need an adult with you, because you are still a baby. But the day you turn 18, you need a kid with you, because otherwise you might be a pervert.