Sam Winchester did not know why it started, or how it started, but he knew when it started. Exactly three weeks and two days from the initiation of the archangel into their death wish club, Dean had gotten it into his thick head that he wanted to trick a Trickster. After many failed attempts and harmless retaliation on Gabriel's part—although filling the Impala entirely with bubbles was not Dean's definition of 'harmless'—his brother had begged Sam to join the cause.
Because, apparently, the cause to save humanity was not enough.
But Dean and Gabriel had reached some sort of truce with their hatred in their attempts (Dean's attempts, Gabriel's success) in pranking each other that Sam was not about to complain. Why had he agreed? Well, Dean had liquored his little brother up before he asked, so Sam knew why he had agreed.
And Sam's mind was a wonderful little bitch when it came to seemingly impossible tasks. He pondered the idea of surprising the archangel so much, he felt he was going to drive himself insane. So, as Dean and Castiel were sitting at a little table in whatever motel room they had hobbled into tonight, and as Gabriel was leaning against the far wall twisting a lollipop between his teeth, his brain must have short-circuited.
Sam strolled three amazingly long steps across the room. Gabriel only had time to quirk an eyebrow in question as Sam stopped right in front of him. The young hunter reached out, plucked the candy from between the archangel's lips, and stuck it in his mouth.
The room was silent.
Gabriel's jaw dropped, his hand still in midair in a past attempt to play with the stick of the lollipop. Honey eyes were probably the widest they have ever been.
Sam just tilted his head slightly and cocked a grin, "Strawberry."
And that was the first time Sam ever saw an angel blush. The red tinge started out over the bridge of Gabriel's nose, reaching up to his ears, and diving down his neck. The archangel disappeared before the sound of a snap even registered in the hunter's mind.
Sam could distantly hear his brother laughing in the background, but he could only concentrate on the empty space that had been occupied by the archangel. The startled expression, the full on flush, seeing Gabriel look like he was absolutely caught off-guard—it caused a warmth to flutter in the depths of the young Winchester's stomach; a feeling he should probably analyze a little more than he actually wanted to.
He pushed the lollipop to the opposite corner of his mouth with his tongue, the sugary juices wrapping around his taste buds. The corner of his lips tilted upward in a small smile as one definite revelation cemented in his mind.
Whatever had just happened, Sam decided that he liked it.