下不來

下 = 一 + 卜 : Mnemonic symbol: from the up/down logic, and a little bit the shape of the character, a ladder.

Xi Shi (xi) is on a retreat in the ashram. Using a voodoo staff (卜), she divined that next (下) week she'll have to play the flute (一) sixteen hours per day. Because she hates playing the flute, she climbs over the ashram's bathroom (a4) wall using a ladder (下) to escape.

不 = 丆 + 卜 : Bruno Bear (bu) is setting up a wind wheel (丆) with a voodoo staff (卜) in the space station's bathroom (Ø4). He also puts a "forbidden" sign (mnemonic symbol for 不) on it, to make clear that it may not (不) be stopped.

來 = 从 + 木 : Mnemonic symbol: mailwoman. Sir Lancelot (l) is visiting the mailwoman (來) in the airplane's kitchen (ai2). As a gift, he brought a Christmas tree (木) decorated with rubber chicken (从).

来 = 丷 + 未 : Mnemonic symbol: mailwoman. Lancelot (l) is super happy that his inflatable crocodile (丷) and live size Ai Weiwei (未) puppet finally arrived (来). The mailwoman (来) delivered them straight to the kitchen of the airplane (ai2).