It's Bears vs. Eagles on the Game Boy. The title pretty much explains the whole plot.
Nintendo's baseball rendition is very similar to Tengen's RBI Baseball series on the NES. However, Nintendo had just beat Tengen in a legal battle and forced them to quit developing for their systems, and decided to try their hand at baseball themselves. The graphics are simple. The Bears wear white clothes, the Eagles wear dark clothes, and that's the difference in the two teams (and as far as I know those are the only two). There are two basic views. Pitching/batting view, in which the batting sequence takes place. When batting, A or B does the same thing (swing the bat). For pitching, combine the control pad with the two buttons for different combos (slow curve, fast curve, fastball, etc). The other view is on the field, where the running takes place. The batting team must run between bases (which they do automatically if possible), and the pitching team has to position his outfielders to catch the ball. The crowd is basically a bunch of little pixels. Light music plays in the background, and sounds are pretty much limited to hitting and catching the ball.
One of the Game Boy's only baseball games, which have become fewer and fewer as time goes on. If you like baseball, or have played the RBI games, this is a good portable version.