diff --git a/addons/calendar/static/src/js/base_calendar.js b/addons/calendar/static/src/js/base_calendar.js
index f2c1e56b298..46362327e17 100644
--- a/addons/calendar/static/src/js/base_calendar.js
+++ b/addons/calendar/static/src/js/base_calendar.js
@@ -8,7 +8,7 @@ var relationalFields = require('web.relational_fields');
 var session = require('web.session');
 var WebClient = require('web.WebClient');
 
-var FieldMany2ManyTags = relationalFields.FieldMany2ManyTags;
+const FieldMany2ManyTagsAvatar = relationalFields.FieldMany2ManyTagsAvatar;
 
 var CalendarNotification = Notification.extend({
     template: "CalendarNotification",
@@ -137,7 +137,7 @@ BasicModel.include({
     },
 });
 
-var Many2ManyAttendee = FieldMany2ManyTags.extend({
+const Many2ManyAttendee = FieldMany2ManyTagsAvatar.extend({
     // as this widget is model dependant (rpc on res.partner), use it in another
     // context probably won't work
     // supportedFieldTypes: ['many2many'],
diff --git a/addons/calendar/static/src/scss/calendar.scss b/addons/calendar/static/src/scss/calendar.scss
index 7e98c95d0ae..4260c9bad73 100644
--- a/addons/calendar/static/src/scss/calendar.scss
+++ b/addons/calendar/static/src/scss/calendar.scss
@@ -3,13 +3,14 @@
     width: 10px;
     height: 10px;
     border-radius: 5px;
+    vertical-align: middle;
 
     &.accepted {
         background-color: theme-color('success');
     }
 
-    &.needsAction {
-        background-color: $o-brand-secondary;
+    &.tentative {
+        background-color: $o-main-color-muted;
     }
 
     &.declined {
diff --git a/addons/calendar/static/src/xml/base_calendar.xml b/addons/calendar/static/src/xml/base_calendar.xml
index 8ecdd17b5fd..f2f30f361f6 100644
--- a/addons/calendar/static/src/xml/base_calendar.xml
+++ b/addons/calendar/static/src/xml/base_calendar.xml
@@ -1,8 +1,9 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <template>
-    <t t-name="Many2ManyAttendeeTag" t-extend="FieldMany2ManyTag">
+    <t t-name="Many2ManyAttendeeTag" t-extend="FieldMany2ManyTagAvatar">
         <t t-jquery="span:first" t-operation="prepend">
-            <span t-if="attendeesData[el_index]" t-attf-class="o_calendar_invitation #{attendeesData[el_index].status}"/>
+            <span t-if="attendeesData[el_index] and attendeesData[el_index].status and attendeesData[el_index].status !== 'needsAction'"
+                t-attf-class="o_calendar_invitation #{attendeesData[el_index].status}"/>
         </t>
     </t>
 
diff --git a/addons/calendar/static/tests/calendar_tests.js b/addons/calendar/static/tests/calendar_tests.js
index 3eea3dff08b..d2626b0ab51 100644
--- a/addons/calendar/static/tests/calendar_tests.js
+++ b/addons/calendar/static/tests/calendar_tests.js
@@ -34,7 +34,7 @@ QUnit.module('calendar', {
     },
 }, function () {
     QUnit.test("many2manyattendee widget: basic rendering", async function (assert) {
-        assert.expect(9);
+        assert.expect(12);
 
         var form = await createView({
             View: FormView,
@@ -55,7 +55,7 @@ QUnit.module('calendar', {
                         "the event id should be passed as argument");
                     return Promise.resolve([
                         [1, "Jesus", "accepted", 0],
-                        [2, "Mahomet", "needsAction", 0],
+                        [2, "Mahomet", "tentative", 0],
                     ]);
                 }
                 return this._super.apply(this, arguments);
@@ -71,8 +71,16 @@ QUnit.module('calendar', {
             "Jesus should attend the meeting");
         assert.strictEqual(form.$('.o_field_widget[name="partner_ids"] .badge[data-id="2"]').text().trim(), "Mahomet",
             "the tag should be correctly named");
-        assert.hasClass(form.$('.o_field_widget[name="partner_ids"] .badge[data-id="2"] .o_calendar_invitation'),'needsAction',
+        assert.hasClass(form.el.querySelector('.o_field_widget[name="partner_ids"] .badge[data-id="2"] .o_calendar_invitation'), 'tentative',
             "Mohamet should still confirm his attendance to the meeting");
+        assert.hasClass(form.el.querySelector('.o_field_many2manytags'), 'avatar',
+            "should have avatar class");
+        assert.containsOnce(form, '.o_field_many2manytags.avatar.o_field_widget .badge:first img',
+            "should have img tag");
+        assert.hasAttrValue(form.$('.o_field_many2manytags.avatar.o_field_widget .badge:first img'),
+            'data-src',
+            '/web/image/partner/1/image_128',
+            "should have correct avatar image");
 
         form.destroy();
     });
diff --git a/addons/calendar/views/calendar_views.xml b/addons/calendar/views/calendar_views.xml
index 2bef5742a86..0126c6fc74c 100644
--- a/addons/calendar/views/calendar_views.xml
+++ b/addons/calendar/views/calendar_views.xml
@@ -257,7 +257,7 @@
                 color="user_id">
                 <field name="attendee_status"/>
                 <field name="user_id" string="Responsible" filters="1" widget="many2one_avatar_user"/>
-                <field name="partner_ids" widget="many2many_tags_avatar" write_model="calendar.contacts" write_field="partner_id" avatar_field="image_128"/>
+                <field name="partner_ids" widget="many2manyattendee" write_model="calendar.contacts" write_field="partner_id" avatar_field="image_128"/>
                 <field name="is_highlighted" invisible="1"/>
                 <field name="description"/>
                 <field name="privacy"/>
diff --git a/addons/web/static/src/js/views/calendar/calendar_popover.js b/addons/web/static/src/js/views/calendar/calendar_popover.js
index 8bfadbc7c4d..3e6c7b8a8ed 100644
--- a/addons/web/static/src/js/views/calendar/calendar_popover.js
+++ b/addons/web/static/src/js/views/calendar/calendar_popover.js
@@ -95,6 +95,27 @@ var CalendarPopover = Widget.extend(WidgetAdapterMixin, StandaloneFieldManagerMi
     // Private
     //--------------------------------------------------------------------------
 
+    /**
+     * Returns the AbstractField specialization that should be used for the
+     * given field informations. If there is no mentioned specific widget to
+     * use, determines one according the field type.
+     *
+     * @private
+     * @param {Object} field
+     * @param {Object} attrs
+     * @returns {function|null} AbstractField specialization Class
+     */
+    _getFieldWidgetClass(field, attrs) {
+        let FieldWidget;
+        if (attrs.widget) {
+            FieldWidget = fieldRegistry.getAny(['form' + "." + attrs.widget, attrs.widget]);
+            if (!FieldWidget) {
+                console.warn("Missing widget: ", attrs.widget, " for field", attrs.name, "of type", field.type);
+            }
+        }
+        return FieldWidget || fieldRegistry.getAny(['form' + "." + field.type, field.type, "abstract"]);
+    },
+
     /**
      * Generate fields to render into popover
      *
@@ -104,11 +125,15 @@ var CalendarPopover = Widget.extend(WidgetAdapterMixin, StandaloneFieldManagerMi
     _processFields: function () {
         var self = this;
         var fieldsToGenerate = [];
+        const fieldInformation = {};
         var fields = _.keys(this.displayFields);
         for (var i=0; i<fields.length; i++) {
             var fieldName = fields[i];
             var displayFieldInfo = self.displayFields[fieldName] || {attrs: {invisible: 1}};
             var fieldInfo = self.fields[fieldName];
+            fieldInformation[fieldName] = {
+                Widget: self._getFieldWidgetClass(fieldInfo, displayFieldInfo.attrs),
+            };
             var field = {
                 name: fieldName,
                 string: displayFieldInfo.attrs.string || fieldInfo.string,
@@ -145,9 +170,12 @@ var CalendarPopover = Widget.extend(WidgetAdapterMixin, StandaloneFieldManagerMi
         };
 
         this.$fieldsList = [];
-        return this.model.makeRecord(this.modelName, fieldsToGenerate).then(function (recordID) {
+        return this.model.makeRecord(this.modelName, fieldsToGenerate, fieldInformation).then(async function (recordID) {
             var defs = [];
 
+            const recordDataPoint = self.model.localData[recordID];
+            recordDataPoint.res_id = self.event.extendedProps.record.id;
+            await self.model._fetchSpecialData(recordDataPoint);
             var record = self.model.get(recordID);
             _.each(fieldsToGenerate, function (field) {
                 if (field.invisible) return;
diff --git a/addons/web/static/tests/views/calendar_tests.js b/addons/web/static/tests/views/calendar_tests.js
index 81475b4e7ed..725fcc9cb53 100644
--- a/addons/web/static/tests/views/calendar_tests.js
+++ b/addons/web/static/tests/views/calendar_tests.js
@@ -2,15 +2,18 @@ odoo.define('web.calendar_tests', function (require) {
 "use strict";
 
 var AbstractStorageService = require('web.AbstractStorageService');
+const BasicModel = require('web.BasicModel');
 var CalendarView = require('web.CalendarView');
 var CalendarRenderer = require('web.CalendarRenderer');
 var Dialog = require('web.Dialog');
+const fieldRegistry = require('web.field_registry');
 var ViewDialogs = require('web.view_dialogs');
 var fieldUtils = require('web.field_utils');
 var mixins = require('web.mixins');
 var RamStorage = require('web.RamStorage');
 var testUtils = require('web.test_utils');
 var session = require('web.session');
+const Widget = require('web.Widget');
 
 var createActionManager = testUtils.createActionManager;
 
@@ -912,6 +915,49 @@ QUnit.module('Views', {
         calendar.destroy();
     });
 
+    QUnit.test('render popover with widget which has specialData attribute', async function (assert) {
+        assert.expect(3);
+
+        await testUtils.mock.patch(BasicModel, {
+            _fetchSpecialDataForMyWidget() {
+                assert.step("_fetchSpecialDataForMyWidget");
+                return Promise.resolve();
+            },
+        });
+
+        const MyWidget = Widget.extend({
+            specialData: "_fetchSpecialDataForMyWidget",
+        });
+
+        fieldRegistry.add('specialWidget', MyWidget);
+
+        const calendar = await createCalendarView({
+            View: CalendarView,
+            model: 'event',
+            data: this.data,
+            arch: `<calendar class="o_calendar_test"
+                    date_start="start"
+                    date_stop="stop"
+                    all_day="allday"
+                    mode="week">
+                        <field name="name" string="Custom Name" widget="specialWidget"/>
+                        <field name="partner_id"/>
+                </calendar>`,
+            archs,
+            viewOptions: {
+                initialDate,
+            },
+        });
+
+        const event4 = document.querySelectorAll(".fc-event")[0];
+        await testUtils.dom.click(event4);
+        assert.containsOnce(calendar, '.o_cw_popover', "should open a popover clicking on event");
+        assert.verifySteps(["_fetchSpecialDataForMyWidget"]);
+
+        calendar.destroy();
+        await testUtils.mock.unpatch(BasicModel);
+    });
+
     QUnit.test('attributes hide_date and hide_time', async function (assert) {
         assert.expect(1);