Kirby's Block Ball

Yeah

This is Brobo's only physical appearance. :(
The Kirby which appears inside the 'O' of the word 'Block' in the English title text is identical to an artwork piece of Spark Kirby from Kirby's Dream Land 2.
If the player manages to earn the high score on Stage 11, a bonus screen is shown, which informs the player of a special bonus for pressing the B button while Kirby is hovering over Stage 11 on the map. When this is done, Kirby moves up to the Sub-Game ring, allowing him to play them at will without accessing them from in the stages themselves.
According to the Kirby's Dream Collection Special Edition's Kirby 20th Anniversary Celebration Book, it was originally planned to represent Kirby as the paddles, rather than the ball.
Kirby's Block Ball is the first Kirby game to include a fire-centered ability (Burning) without an ice-centered counterpart (such as Freeze).
Sprites for Pengy and Waddle Doo can be found in the game's files, including a defeat sprite of Waddle Doo losing his eye. Pengy and Waddle Doo also appear in the instruction booklet for the game, implying that they were cut fairly late in development.

Pengy's graphics are loaded in Area 2 of Stage 7.
The game's instruction manual depicts artwork of the two enemies alongside Propeller, Chuckie, Coner, and Slippy. This suggests that Waddle Doo and Pengy were cut late in development.

Kirby's Block Ball has the fewest Copy Abilities of any game that has them, with only four.
Kirby's Block Ball is the only known Kirby game to have been made in collaboration with Tose, a Japanese game developer with a hand in over 1000 games, who would later create the original series The Legendary Starfy. As with most of their projects, they are not named in the game's credits. Nevertheless, the list shares several staff members with Tose's Game & Watch Gallery series, among other Tose games.
Kirby's Block Ball was one of the last games to have Game Boy hardware designer Gunpei Yokoi in the role of producer, before his departure from Nintendo in 1996 and his death in 1997.