In order to make your motion graphics transition flow smoothly you will need to add iMovie transitions to the beginning and ending of the motion graphics clip.

Click the transition button to change to the Transitions Pane. Choose a transition by clicking on it in the list that appears. In our example we chose an Overlap transition.

Set the timing of the iMovie transition so that it will take up half of the transition clip and give enough overlap for the clip that precedes it. Since the Pastel kaleida clip was one second in length, we set the Overlap transition timing for 25 frames, half covering the Leonard Nimoy clip and half covering the Pastel kaleida transition clip.

Once the settings are adjusted to your liking click and drag the transition to the timeline and release it between the first video segment and the motion graphics transition.

Repeat the process for transitioning out of the motion graphics clip by draging the same iMovie transition to the end of that clip.

Play the transition and adjust timing of the transitions as necessary.

Now you have a very flashy way to segue between Leonard Nimoy and Steve Balmer, and to be honest anything less would not be appropriate for such an unholy pairing of video clips.