8
Tim's parents go with Francis to Las Vegas, and Francis has his brother Eugene (Conrad Vernon) pose as Tim and Boss Baby's babysitter to keep them from interfering. Without a steady flow of serum to keep his intelligence in check, Boss Baby begins reverting back to being a normal baby. Despite this, he and Tim manage to evade the "babysitter" long enough to get to the airport, but are too late to intercept Tim's parents. Upset, Tim blames Boss Baby for using his family for his own ulterior motives, for which Boss Baby, after some hesitance, apologizes. After sneaking on a plane for Elvis impersonators (James McGrath and James Izzo) bound for Vegas, they stall Francis' presentation when Eugene (disguised as another Elvis impersonator) unwittingly gives away their plan, which they begin to have a good time together with Tim's imagination in the plane.
Furious at their interference, Francis proceeds to lock Tim's parents up so he can burn them with exhaust from a rocket used to launch the Forever Puppies. Tim and Boss Baby fight with him, and then push him into the formula. Boss Baby opens the rocket to let the dogs out, so they can save Tim's parents. After he successfully does that, he returns to baby state while still on the rocket, but Tim sings to him with a family song to show his appreciation, causing him to jump off of the rocket before it launches. Francis, having reverted back to baby form, attempts to attack them again, but Eugene interferes, stating he'll "raise him right this time" now that he's a baby again. Boss Baby gets promoted, leaves in a taxi, and Tim goes back to being an only child. But Tim and Boss Baby, having grown closer, start to miss each other (which they discover that love don't change places but multiples instant). Boss Baby, fed up, decides to be part of the Templeton family permanently. He returns to the Templeton family as a regular baby named Theodore Lindsey, as the whole story turned out to be in Tim's imagination, and Ted and Janice have just brought him home from the hospital.