I suppose it's because extbob should be a variable. So if I declare it before AnimeIVTC script it works.
Code:
bobclp=BlankClip(length=240, width=1440, height=480, pixel_type="YV12", fps=29.970, fps_denominator=1, audio_rate=44100, channels=1, sample_type="8bit", color=$000000).MC_A_bob()
BlankClip(length=240, width=1440, height=480, pixel_type="YV12", fps=29.970, fps_denominator=1, audio_rate=44100, channels=1, sample_type="8bit", color=$000000).AnimeIVTC(2, killcomb=1, bbob=5, extbob=bobclp)