highest / greatest / too (much) / very / extremely
太
=
丶
+
大
:
Mnemonic symbol: from 太后 [tai4 hou4], the empress dowager. The empress dowager prepares for her reign in the airplane's bathroom (ai4) and has a big robot (大) as well as Tecumseh (t) fan her fresh air with petal leaves (丶).
沟
=
勾
+
氵
:
In front of the outhouse (ou1) Guy Fawkes (g) drew (勾) a photo-realistic comic (勾) of an open gully (沟) on the floor. The people are afraid to step onto it because it looks so real. They only start to believe Guy Fawkes that it's not as he spills a bottle of water (氵) over his chalk painting.