Conversation so far:
What happened in the 2000's?
Peele regularly performed at Boom Chicago in Amsterdam and The Second City in Chicago.
What did he do on Mad Tv?
Peele performed celebrity impersonations.
Who did he impersonate?
Caroll Spinney (as the voice of Big Bird from Sesame Street), Ja Rule, James Brown, Flavor Flav, Justin Guarini, Montel Williams, Morgan Freeman and Forest Whitaker.
Did he do anything else on Mad?
Peele was nominated for a 2008 Emmy Award for his song "Sad Fitty Cent", a music video parody about 50 Cent lamenting over his rivalry with Kanye West.
What did he do before Mad?
Peele regularly performed at Boom Chicago in Amsterdam and The Second City in Chicago.

Question: What was his act?
Self-contained rewrite: What was Jordan Peele's act at Boom Chicago in Amsterdam and The Second City in Chicago?