The secret reason that the Boggle letters were changed

First introduced in 1972, Boggle is a delightful game in which you try to find words on a grid of shaken dice (with each die having six letters on it). In 1987, manufacturer Parker Brothers quietly updated the game by changing which letters were on which die. One reason could be that the the new lettering generated more words a player could find, increasing excitement in the game. But at Now I Know, Dan Lewis lays out another possible motivation for the secret switch:

This is pure speculation (but I think you'll agree): there are a few words you simply can't spell out in the newer version of Boggle. The reason why? The AFFKPS cube.

Pre-1987, the game had two Ks and two Fs. Those letters appeared on four different dice, as listed above: BIFORX and EEFHIY contained the Fs, while DKNOUT and EGKLUY contained the Ks. As a result, you could spell words like "FORK," or, as seen above, "KNIFE," provided that the cubes fell in a manner that made those words available. 

The 1987 revision, though, removed the ability for players to discover those cutlery-related words. To spell either "FORK" or "KNIFE," you need to roll the dice in such a way that both an F and a K are present on the 4×4 board. But the only Fs and Ks available in the revised version of the game are on the same cube — the AFFKPS one. It is impossible, therefore, to spell any word that requires both an F and a K, such as fork, knife, or… 

(via Kottke)