d08d7ae4_ifetime_reward___The_Sims_Wiki__Description
[Lifetime reward] My Best Friend [Cost] 40,000 [Available] Child [Notes] A random gendered Sim robot instantly joins the family with instant and permanent best friend status to the rewarded Sim. Simbots can also be made from the Inventing skill. [Description] 
A SimBot joins the family with Best Friend relationship status to the Sim who chooses this lifetime reward.
Lifetime reward - The Sims Wiki