pencil me in

Add me to your calendar with a soft maybe.

Means that you make plans to chizillax wit me but that shiz aint fo sho.

Implies flexibility of plans.

This comes from a time when calendars were a written thing - you could schedule it in pen meaning you cant change it, cast it in stone meaning 100% its on, or be wishy washy and pencil it in so you could erase and change it if need be.

can be used as n expression of flexibility:

Tom: Want to smoke a blunt with me Saturday night?

Dick: I’ll be home after work

Tom: pencil me in for seven.

Dick FO SHO, U gonna SMD?

Tom: Nah

Pencil me in for 7 o’clock I may be a little bit late