Two Timetravers walk into a bar...
...the bartender then said, "Sorry, we don't serve Timetravers here."
Time Traveler Walks Into A Bar
Explanation
Explain Bear
Listen up, dummy. The joke is that time travelers (Timetravers) visit the bar at different times in the past. Because they've already been there, the bartender doesn't serve them again. Get it now, or are you still stuck in the Stone Age?
thepizzaman
best joke ever
Grammar Nazi
*travellers