Choosing certain screen names at the beginning of the game will unlock unique profile pictures as well some special messages and responses from Emily:
• Flowey - Unlocks a profile picture of Flowey from Undertale and allows the player to use his quotes from Undertale in the beginning of the game.
• Doge - Unlocks a profile picture of Doge, and will make Emily say "Very icon. Such cool" at the beginning the game.
• Clippy - Unlocks a profile picture of Clippy, the default Microsoft Office Assistant and allows the player to use quotes Clippy normally says in Microsoft Office during the beginning of the game.
• NyanCat - Unlocks the Nyan Cat profile picture and will make Emily ask the player how the Nyan Cat song lyrics go during the beginning of the game.
• Kappa - Unlocks a profile picture of Kappa and will make Emily say "In Kappa we trust" at the beginning of the game.
• Portal - Unlocks a profile picture for Portal and will cause Emily to say "Hello test subject 1209 this experiment will test the emotional imbalances of human teenagers and at the end, there will be a party with cake! :)" at the beginning of the game.
• Hyrule - Unlocks a profile picture of the Triforce from The Legend of Zelda series and will make Emily say "Its dangerous to go alone. Take this! Oops, not sure that helped" once you begin the game.
• Dota - Unlocks the Dota profile picture and let's the player choose unique messages in the beginning of the game.

If the player begins the game, enters their username as "JohnCena", and then chooses the "hey" option, Emily will ask about your name. The player will automatically respond:

my name is JOOOHN CEEEENAAAA
naa na na naaa

This is a reference to professional wrestler John Cena, who became an Internet meme involving videos announcing his name and playing his theme song "The Time Is Now".