If I reveal Here to Help and play Blitzcrank during a showdown while another combat is happening, does Blitz pull the attacking unit immediately?

Ruling: Blitzcrank's trigger does not resolve immediately. The unit enters play immediately, but the trigger goes on the chain and offers responses. The pulled unit will still receive benefits from any effects already on the chain (like Primal Strength). The new combat will stage until the original showdown is complete, and begin immediately afterward.

Sequence:

• Here to Help resolves and Blitzcrank is played
• Blitzcrank enters play immediately
• Blitzcrank's trigger goes on the chain and offers responses
• Original chain completes (including Primal Strength buffing Pit Rookie)
• Blitzcrank's trigger resolves, pulling the unit
• New combat stages and begins after original showdown completes

Nuances:

• Triggered abilities can be placed on chains
• The pulled unit retains buffs from effects that were already on the chain before the pull trigger resolved