Mark Trail: I forgot to tell you, Mark, an old friend of yours, Tim Moore, wanted you to call him!

Mark is apparently so stupid that he doesn't know who his old friends are unless Cherry explicitly reminds him.

This is not surprising, given Mark's less than stellar people skills.

Mark Trail: Guns...that's not good...we'd better get out of here!

Who is Rusty talking to? The dog? Given the humorous expression of surprise on her face in the last panel, the dog can apparently recognize what guns are, so maybe she can understand vast quantities of human language, too. In which case, Rusty really ought to think about entering her in some sort of talent contest.