The start menu has the typical “Press START to Continue”. Pressing start allows you to proceed to the menu, but pressing any other button causes GLaDOS’ voice to come out and say degrading things such as:
“That’s not the start button. I suppose you failed kindergarten a few times.”
“Your mother must be so proud to have raised an ignoramus.”
“*slow clap* you’re still trying.”
“Congratulations - you’ve earned a lifetime in the room of screaming robots.”
“I may as well help you proceed since you can’t do it by yourself.”
“This is almost painful to watch.”
After pressing any other button and then the start button, GLaDOS says “Finally we can begin” in a condescending tone.