Stephen Colbert (pronounced Coll-bair) is an American political satirist, writer, comedian, television host, and actor. He is the host of Comedy Central's The Colbert Report, a satirical spin-off from The Daily Show in which Colbert portrays a caricatured version of conservative political pundits, focusing on a fictional anchorman who is a "well-intentioned, poorly informed, high-status idiot." You can watch the show regularly here.

Floyd Mayweather Jr. is an American professional boxer, a five-division world champion, having won eight world titles in three different weight classes. He is probably the most successful boxer of all time, money-wise, having earned more than $350 million in his career so far. We do not know about a chess connection (except that he has said that "boxing is more like chess" on a MSNBC talkshow) and assume that he appeared in this Colbert show cameo as a tongue-in-cheek jest. Jump forward to 2 min 25 sec to get to the chess bit:

For the record – and for your pleasure – here is the memorable April 2012 appearance of Magnus Carlsen on the Colbert Report (a full ChessBase report is here):

Higlights from Mayweather's boxing career

And if you are looking (and have the nerves) for something bizarre here is Floyd Mayweather doing a Wrestlemania mega-show. Youtube has more in this vein.