p orbitals of C4H6.
Here are the bond lengths of the molecule Here are the bond lengths of the molecule. You see the double bond character at the two ends and the center bond is a little shorter than a single bond but not a double bond. You see that the two filled orbitals both have p bonds at the two ends but only one has a p bond in the middle. Shown below are a single bond and double molecule for comparisons.
Here is a double bond 1.326 Angstrums long
Here is what a single bond looks like (1.5 Angstrums long).
p orbital 0 nodes
p orbital 1 nodes
p orbital 2 nodes
p orbital 3 nodes