Mycroft did in fact steal Sherlock's Action Man.
"My'roft! Gimme it back!"
"Not until you pronounce my name correctly, Shirley. You are five now, aren't you?" Mycroft chuckled as he held the plastic replica of a man high above his head. His brother jumping up as high as he could to try and reach it. "Tut tut, Shirley. It's just a toy."
"I hate you, My'roft." Sherlock sulked, crossing his arms. "Gimme back my action man! We have to go on a mission!"
"I won't be giving it back, Shirley." Mycroft smirked before placing it on top of the high cabinet.
"Then I'm telling Mummy!" Sherlock yelled before running off in search of his mother. Picking up his book, Mycroft sat down knowing he had at least time to read 3 pages.
Sherlock ran back into the room and jumped on top of him. An arrogant smile plastered on his face. As he glanced back towards the door the figure of Mama Holmes appeared. Frowning towards the direction of Mycroft before walking over to the cabinet and bringing the action man to a now gleeful Sherlock. "I told you, Mycroft Holmes. Stop taking your brother's toys."
"I promise, Mummy."
Mycroft chuckled to himself as he watched the monitor. John Watson was entering the black car again for another countless time.
Mycroft Holmes could never keep promises well.