Stephen Colbert has been doing everything from hanging out with Mitt Romney to appearing on public access television to promote next month’s launch of The Late Show with Stephen Colbert.

On Sunday, he rallied about 600 fans in New York’s Union Square for what is thought to be his latest promo. Based on social media accounts, the event featured Colbert speaking to the crowd over a megaphone from the back of a truck and the fans holding balloons in the air and cheering.

Colbert’s Late Show will premiere on Sept. 8. Jeb Bush and George Clooney will be his first guests.

Get The Brief. Sign up to receive the top stories you need to know right now. Please enter a valid email address. Sign Up Now Check the box if you do not wish to receive promotional offers via email from TIME. You can unsubscribe at any time. By signing up you are agreeing to our Terms of Use and Privacy Policy . This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply. Thank you! For your security, we've sent a confirmation email to the address you entered. Click the link to confirm your subscription and begin receiving our newsletters. If you don't get the confirmation within 10 minutes, please check your spam folder.

Write to Justin Worland at justin.worland@time.com.