Twiki was the little robot character from the excellent Sci Fi TV series Buck Rogers in the 25th Century (1979 – 1981 NBC-TV) and also the 1979 movie with the same title that was a lead in to the TV series.
The Twiki suit was worn by Felix Silla who also played Cousin Itt on the Addams Family. The voice of Twiki was Looney Tunes cartoon legend Mel Blanc.
I recently saw the Twiki costume here in Seattle which was pretty cool. Paul Allen co-founder of Microsoft has an incredible Sci Fi collection and Twiki is currently displayed at his Cinerama downtown.
Deano In America 
I totally remember this creepy little bastard!
Even more so up close!