Did it look like this:

https://en.wikipedia.org/wiki/Big_Trak

Doesn't have a pen, but maybe it was a modified version of that toy?

YES! This was exactly it. Thank you.

It seems my pen memory came from a different logo-driven bot. In-fact, the Big Trak was not even Logo-driven, but had a similar command system.

I appear to have combined childhood recollections, but that was the shape I was "remembering." No wonder, just look at that thing! lol