Welp, it's cannon! Spike's penis does NOT have two heads, nor does it look like a gross lizard dick, like in almost all porn of him. YES! =D

Downside is it's a bit too small. Oh well. It beats it being too big like lot of porn tends to do to cartoon penises.

Actually, looking at it again, what appears to be the shaft part is just a shadow. So, all we see is just the very tip of the head. So it may very well could look like a lizard dick. But, it doesn't look like it has two heads, thought if it did, it's possible that the other head is hidden out of sight under spike's belly.