Stephen Colbert by Martin Crook/Comedy Central Stephen Colbert by Martin Crook/Comedy Central

Democratic presidential candidate Hillary Clinton appears on The Colbert Report (11:30 pm/ET, Comedy Central) on Thursday.

Her Democratic opponent, Barack Obama, has declined Colbert's invitations, though his wife, Michelle, is slated to appear tonight.

The Colbert Report orignates from Philadelphia this week in advance of next Tuesday's Pennsylvania Democratic primary. - J.R. Whalen