I don't understand why this is mest rather than flest. Is it to do with legetøj being the same for singular and plural in Danish - ie are they treated as an uncountable mass?
It is explained in the tips and notes: mest is used for amounts, flest for counting. Which confuses me a bit, because I think toys can be counted. But maybe in this context the exact number of toys is not known.
legetøj is an uncountable noun in Danish i do not know why but it behaves like water or sand. (No en/et legetøj and no plural)
You can make it countable by adding "stykker" (pieces)
Hun har flest stykker legetøj
"toy(s)" is uncountable also in German.
The boy wins!