Beefy Bert is a supporting character in the Horrid Henry book series and TV series. Bert is a member of the Purple Hand Gang and a close friend of Horrid Henry. And of course, the only word he says is "I dunno". But however in some episodes, there have been exceptions. For example, in the Series 1 TV episode, Horrid Henry Gets Rich Quick, he says "Have you got any food?" and in the Series 4 episode Horrid Henry Who's Who?, after switching personalities with Brainy Brian, he gives his answers in full sentences.
Bert appears in All Star Smashers as a Support Spirit, as an Ace class, where you must fight Brad Till at Henry's House to obtain him. When fighting Brad, he will be heavier, slower, and has increased power. As for the other important things to take note of, I dunno... I just dunno.