Thank you Message
Once you have completed an interview, it is important to send a follow-up a few days later to thank e interviewer for their time. I imagine some candidates may send a physical thank you letter, but I feel a short e-mail is more appropriate especially since delivering an e-mail is immediate compared to a physical letter. It would be awkward if you were rejected, and then your thank you letter arrived late.
For my internship at Disney, the turnaround time to hear back was relatively short, as there were only eight people to interview for two design positions. Therefore I felt an e-mail would definitely suffice in this circumstance - especially since my manager had already contacted me via e-mail with a design task that I needed to complete prior to the interview.
I wrote a message that was short and sweet, making sure to remember the names of the two people who interviewed me. I would write another e-mail such as this in future, after an interview.