Consider doing something fun with reactions.

[phallstrom]

RBot::Bot.instance.on "reaction_added", ->(client, data) do
  client.logger.debug "REACTION ADDED: #{data.inspect}"
end

DEBUG -- SlackRubyBot::Client#dispatch: channel=C094SD96X, 
  channel_type=C, event_ts=1518328447.000037, 
  team=T05052K3Q, ts=1518328447.000037, 
  type=member_joined_channel, user=U054D8V3L

DEBUG -- : REACTION ADDED: #<Slack::Messages::Message event_ts="1518365056.000092" 
item=#<Slack::Messages::Message channel="C5X2E7C8M" ts="1518152536.000117" type="message"> 
item_user="U3GUKJJ2G" reaction="tada" ts="1518365056.000092" 
type="reaction_added" user="U4A1YHS91">