Actually, I can explain that one.

When the Montage video was linked to on Bounceme, I linked to the Oingo Boingo video saying that if you turn off the sound on the montage & listen to the Oingo Boingo video as the background music instead, it's much more entertaining.

Same referrer on different videos = related; either that or the same IPs visiting both videos in a short span of time. It's probably a low-priority criteria, so on a higher-traffic video you wouldn't be able to noticeably influence it that way.