The game's title screen was changed significantly when localized internationally. The background was likely removed to accommodate the larger title text.
The bosses Lololo & Lalala from the second level (Castle Lololo) are based on Lolo and Lala from the Eggerland series.
The reason why Kirby is colored white in the American cover for Kirby's Dream Land is because Nintendo of Japan was having a debate on Kirby's color - which was pink or yellow. The game's creator Sakuri wanted pink, but Shigeru Miyamoto thought yellow would be better. Sakuri's eventually won the debate. However, Nintendo of America didn't know if Kirby was pink or yellow at the time of making the box art, so they decided to play it safe and make Kirby white like he appears in the game.
By waiting for 20 seconds on the pause screen, Kirby will dance. This only happens once for every time you pause the game, and can only be seen again by unpausing the game, pausing it again, and waiting another 20 seconds.