This is Fun level 2, "Floaters all the way". You have 4 lemmings and have to save all of them. You only have 1 minute, but you aren't going to run out of time.
Let's go! The first thing to pay attention to about this level is there are four entrances instead of one! Each entrance will only have one lemming enter through it. Problem is, three of these entrances are too high and the lemmings will fall to their death.
The first lemming will come out the lower door. You need to change him into a Basher as soon as he reaches the wall to the right of him.
As your first lemming is digging, quickly switch over to the Floater ability using L1. A lemming will fall out the second entrance. The first lemming will pick up a Floater ability just in time. Quickly make the falling lemming into a floater.
As the two lemming walk right, they will pick up another Floater ability. A lemming will fall out the third entrance, so use that on him before he hits the ground.
Once again, you will pick up one last Floater. Use this on the lemming that falls out the fourth entrance.
All your lemmings will them exit safely.
Success! Press X to continue to the third Fun level.