Uh...run!

WWYDI you were riding for Narnia and the North and your three companions (yes, the horses are companions) up and deserted you? (Not that they would, but what if they did?)

Yup, I'd definitely despair! What I'd do after that, I've no idea....

Wwydi, one morning, a bird gave you a bright berry that looks rather more like a live coal?

Tell him thank you very much, but I'm not a star and I think my lot in life is to grow older, not younger.

WWYDI TLC was deleted. Forever.

I'd assume the rest of the internet mysteriously disappeared as well. Then I'd go a café to see what people would do if their phones weren't working.

WWYDI you saw Glimfeather at a Cair Paravel council meeting that was happening during the day?

Wonder what he was doing up at such a...late/early hour. Other than that, nothing really.

WWYDI you woke up tomorrow in a world where Narnia does not exist?

*clears throat* "I'm going to live as like a Narnian as I can even if there isn't any Narnia." 😛
Okay, maybe not quite, but I'll be holding onto Narnia very tightly. 😀

WWYDI an Owl offered to give you a ride?

An owl or an Owl? If the former, I'd freak out. If the latter, well, it'd depend on the circumstances. If there were such circumstances that I would need to take a ride with an Owl, I'd accept, of course. If not, I'd also freak out, though in a different way.

WWYDI you found out Narnia and LotR are actually in the same universe... (wait WHAT?!)

*mind....blown* I want to go more!

WWYDI you found yourself outside Trufflehunter's, Trumpkin's, and Nikabrik's home?

I'll go and hide there with 'em. If I were to get caught, you know whose side I'd be on...and plus I don't wanna get struck by lightning/a tree falling down.

WWYDI you found yourself in the train station in LWW with the Pevensies?

Probably wish I could feasibly follow them to Digory's place and tag along with them into Narnia. 😉

WWYDI you found Susan's horn?

Hide it. Maybe tell a few friends. Then keep it until some nation somewheres announces they will throw a nuke at some other nation, and then I'd blow it.
On second thoughts, when would they ever warn people beforehand? 🙁

WWYDI you met Father Christmas?

(Heh, point.)

Probably be more excited than I think I'd be. 😉

WWYDI you turned a corner and ran into Glenstorm?

Say "howdy" and walk on my merry way.

WWYDI you turned a corner and saw your second-favorite character?

Try to behave like a normal person... I like Peter a great deal and he's a king besides!

WWYDI you found an under-tree dwelling like Trufflehunter's in our world?

Lean in and say "hi" if Truff is there. If Nikabrik is there I'd be a bit nervous...

WWYDI you met your third-favorite character at the grocery store?