11 can do whatever he wants:

Wear a Fez and Bowtie: Because Bowties and Fezzes are cool!

Eats fish fingers and custard: Not something that we humans imagine would go together. But who cares? 11 likes it!

Cross into his own timestream: Don't tell the Time Lords!...Oh right! They're dead. (or are they?)

Invite himself to his own death: Because he can!

Marry the child of your companion: Let's face it, that was slated to happen at some point.