WATCH: 'Eyes'... the riddle that just keeps on giving
There's nothing like an early morning riddle to get the cogs in your brain clunking.
What does 'y-e-s' spell?
Now, add an 'e' to the beginning and see if anyone falls for it.
Couple Tom and Libby, otherwise known as the Mongol Rally duo, have got the internet talking with the latest riddle.
The pair are raising funds for charity as they get set to drive 10,000 miles to Mongolia with no navigation or assistance.
In the meantime, they're entertaining Facebook with their antics and pranks.
"I actually can't believe my girlfriend fell for this!" Tom wrote under the post.