From Tekkenpedia

Head Butt Carnival
Command	f,f+1+4
Stance
Damage	29 (T3) 33 (TTT onwards)
Hit Range	T!
Properties

Head Butt Carnival is a secret moves for Heihachi Mishima introduced in Tekken 3. Originally this move could only be performed against Jin, Heihachi, Lei and Kuma. In Tekken Tag Tournament it can be performed against all the listed Tekken 3 characters and Kazuya, Jack 2, Gun Jack and Prototype Jack. In Tekken 4 it can be performed on the listed Tekken 3 characters, Paul and Bryan. After Tekken 5 it can be performed on all male opponents and Panda. The exceptions are Ganryu and Eddy.

Head Butt Carnival bears resemblence to the move Stone Head (f,f+1+2), the damage, escape are exactly the same and the animation is very similar. The difference in animation is, instead of the opponent being knocked to the ground, they are pushed away and electricity surrounds Heihachi's head.

[edit] Escape and Reversals

The escape to this move is 1+2. This move can also be reversed by pressing 1 or 2 which does 30 unblockable damage. In turn Heihachi can reverse the reversal with 1+2, which in turn can be reversed with 1 or 2. This sequence can potentially last infinitely.