Procrastination is Key.

Leonard: You won't believe what just happened...!

Sheldon: You went out in the hallway, stumbled into an inter-dimensional portal, which brought you five thousand years into the future. There you took advantage of the advanced technology to build a time machine. Now you're back to bring us all with you to the year 7010 where we are all transported to work at the Thinkatorium by telepathically controlled flying dolphins.

Leonard: Uh, no.